LAKHMIR SINGH AND MANJIT KAUR Solutions for Class 10 Chemistry Chapter 3 - Metals and Non-metals

Chapter 3 - Metals and Non-metals Exercise 131

Question 1

Name one material and one non-metal which exist in liquid state at room temperature.

Solution 1

Metal - Mercury.

Non metal - Bromine.

Question 2

Why are metals called electropositive elements whereas non-metals are called electronegative elements?

Solution 2

Metals are electropositive elements because they can form positive ions by losing electrons.

Non-metals are electronegative elements because they can form negative ions by gaining electrons.

Question 3

(a)Name the most abundant metal in the earth's crust.

(b)Name the most abundant non-metal in the earth's crust.

Solution 3

(a) Aluminium.

(b) Oxygen.

Chapter 3 - Metals and Non-metals Exercise 132

Question 4

Name one metal which has a low melting point.

Solution 4

Cesium.

Question 5

Name the metal which is the poorest conductor of heat.

Solution 5

Lead.

Question 6

State whether the following statement is true or false:

Non-metals react with dilute acids to produce a gas which burns with a pop sound.

Solution 6

False.

Question 7

From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal:

(i)Which reacts with water only on boiling, and

(ii)Another which does not react even with steam.

Solution 7

(i) Aluminium.

(ii) Copper.

Question 8

What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?

Solution 8

Iron nail gets covered with a red-brown coating of copper metal; The blue colour of copper sulphate solution fades gradually.

Question 9

What is aqua-regia? Name two special metals which are insoluble in common reagents but dissolve in aqua-regia.

Solution 9

Aqua-regia is a freshly prepared mixture of one part of concentrated nitric acid and 3 parts of concentrated hydrochloric acid. Gold and platinum dissolve in aqua-regia

Question 10

Give the names and formulae of (a) two acidic oxides, and (b) two basic oxides.

Solution 10

(a) Carbon dioxide and sulphur dioxide.

(b) Sodium oxide and magnesium oxide.

Question 11

What name is given to those metal oxides which show basic as well as acidic behaviour?

Solution 11

Amphoteric oxides.

Question 12

Name two metals which form amphoteric oxides.

Solution 12

Aluminium and zinc.

Question 13

A copper coin is kept immersed in a solution of silver nitrate for some time. What will happen to the coin and the colour of the solution?

Solution 13

Copper coin will get a shining greyish white coating of silver metal. The color of the solution will turn blue.

Question 14

Which property of copper and aluminium makes them suitable:

(a)For making cooking utensils and boilers?

(b)For making electric wires?

Solution 14

(a) High thermal conductivity.

(b) High electrical conductivity.

Question 15

Write the names and formulae of (a) a metal hydride, and (b) a non-metal hydride.

Solution 15

Sodium hydride, NaH

Hydrogen sulphide, H2S

Question 16

Name the metal which has been placed:

(a)At the bottom of the reactivity series

(b)At the top of the reactivity series

(c)Just below copper in the reactivity series

Solution 16

(a) Gold.

(b) Potassium.

(c) Mercury.

Question 17

Which of the two metals is more reactive: copper or silver?

Solution 17

Copper.

Question 18

(a)Name one metal which is stored in kerosene oil.

(b)Name one non-metal which is stored under water.

Solution 18

(a) Sodium.

(b) White phosphorus.

Question 19

Write equation for the reaction of:

(a)Sodium with oxygen

(b)Magnesium with oxygen

Solution 19

(a)


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b)


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 20

Name two metals which are used:

(a)For making electric wires.

(b)For making domestic utensils and factory equipment.

(c)For making jewellery and to decorate sweets.

Solution 20

(a) Aluminium and copper.

(b) Copper and aluminium.

(c) Gold and silver.

Question 21

Which metal foil is used for packing some of the medicine tablets?

Solution 21

Aluminium foil.

Question 22

Name the non-metal which is used:

(a)To convert vegetable oil into vegetable ghee (solid fat).

(b)As a rocket fuel (in liquid form).

(c)To make electrodes of dry cells.

(d)To preserve food materials.

(e)In the vulcanization of rubber.

Solution 22

(a) Hydrogen.

(b) Hydrogen.

(c) Carbon.

(d) Nitrogen.

(e) Sulphur.

Question 23

Name one property which is characteristic of (a) metals, and (b) non-metals.

Solution 23

(a) Metals are malleable.

(b) Non-metals are non-malleable.

Question 24

What is meant by "brittleness"? Which type of elements usually show brittleness: metals or non-materials?

Solution 24

Brittleness is the property of being brittle i.e. breaking easily.

Non-metals show brittleness.

Question 25

What will happen if a strip of zinc is immersed in a solution of copper sulphate?

Solution 25

When a strip of zinc metal is put in copper sulphate solution, then the blue colour of copper sulphate solution fades gradually and red brown coating of copper is deposited on zinc strip.

Question 26

What will happen if a strip of copper is kept immersed in a solution of silver nitrate (AgNO3)?

Solution 26

When a strip of copper metal is immersed in silver nitrate solution, the solution gradually becomes blue and a shining greyish-white deposit of silver metal is formed on copper strip.

Question 27

What happens when iron nails are put into copper sulphate solution?

Solution 27

When iron nails are placed in copper sulphate solution, the blue colour of copper sulphate solution fades gradually and red-brown copper metal is formed.

Question 28

How would you show that silver is chemically less reactive than copper?

Solution 28

If a strip of silver metal is kept immersed in copper sulphate solution for some time, then no reaction occurs. This shows that silver is not able to displace copper from copper sulphate solution.

Question 29

Give reasons for the following:

Blue colour of copper sulphate solution is destroyed when iron fillings are added to it.

Solution 29

Blue color of copper sulphate is destroyed because iron displaces copper from copper sulphate solution as iron is more reactive than copper.

Chapter 3 - Metals and Non-metals Exercise 133

Question 30

Name a non-metal having a very high melting point.

Solution 30

Diamond.

Question 31

Which property of graphite is utilized in making electrodes?

Solution 31

Since graphite is a good conductor of electricity, it is used in making electrodes.

Question 32

Name two non-metals which are both brittle and non-ductile.

Solution 32

Sulphur and phosphorus.

Question 33

Explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.

Solution 33

The surface of some metals acquires a dull appearance when exposed to air for a long time because metals form a thin layer of oxides, carbonates or sulphide on their surface by the slow action of various gases present in air.

Question 34

Complete and balance the following equations:


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Solution 34


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 35

Fill in the following blanks with suitable words:

(a) Magnesium liberates ________ gas on reacting with hot boiling water.

(b) The white powder formed when magnesium ribbon burns in oxygen is of ________.

(c) Ordinary aluminium stripes are not attacked by water because of the presence of a layer of ________ on the surface of aluminium.

(d) A metal having low melting point is ________ but a non-metal having very high melting point is ________.

(e) Calcium is a ________ reactive metal than sodium.

Solution 35

(a) Hydrogen.

(b) Magnesium oxide.

(c) Aluminium oxide.

(d) Sodium; Diamond.

(e) Less.

Question 36

(a)What is meant by saying that the metals are malleable and ductile? Explain with examples.

(b)Name two metals which are both malleable and ductile.

(c)Which property of iron metal is utilized in producing iron sheets required for making buckets?

(d)Which property of copper metal is utilized in making thin wires?

Solution 36

(a) Metals are malleable i.e. they can be beaten into thin sheets with a hammer.

Example: Aluminium.

Metals are ductile i.e. they can be drawn into thin wires.

Example: Copper.

(b) Aluminium and copper.

(c) Malleability.

(d) Ductility.

Question 37

Name two metals which react violently with cold water. Write any three observations you would make when such a metal is dropped into water. How would you identify the gas evolved, if any, during the reaction?

Solution 37

Sodium and potassium metals react violently with cold water.

Observations:

1. Metal starts moving over the surface of water making a hissing sound.

2. Metal starts reacting with water causing little explosions.

3. Soon the metal catches fire and starts burning.

If the gas evolved burns with a 'pop' sound, it indicates that it is hydrogen gas.

Question 38

(a)With the help of examples, describe how metal oxides differ from non-metal oxides.

(b)Which of the following elements would yield: (i) an acidic oxide, (ii) a basic oxide, and (iii) a neutral oxide?

Na, S, C, K, H

Solution 38

(a) Metal oxides are basic in nature and turn red litmus blue. For example: Magnesium oxide.

Non-metal oxides are acidic or neutral in nature. The acidic oxides turn blue litmus red. For example: Carbon dioxide.

(b) (i) Acidic oxide: S, C

      (ii) Basic oxide: Na, K

      (iii) Neutral oxide: H

Question 39

(a)What are amphoteric oxides? Give two examples of amphoteric oxides.

(b)Choose the acidic oxides, basic oxides and neutral oxides from the following:

        Na2O; CO2; CO; SO2; MgO; N2O; H2O

(c)Which of the following are amphoteric oxides:

    Mgo, ZnO, P2O3, Al2O3, NO2

Solution 39

(a) Those metal oxides which show basic as well as acidic behavior are known as amphoteric oxides.

Example: Aluminium oxide and zinc oxide.

(b) Acidic oxide - CO2, CO, SO2 and N2O; Basic oxide - Na2O, MgO; Neutral oxide - H2O.

(c) ZnO, Al2O3.

Question 40

(a)What is the nature of the oxide SO2? What happens when it is dissolved in water? Write the chemical equation of the reaction involved.

(b)What is the nature of the oxide Na2O? What happens when it is dissolved in water? Write the chemical equation of the reaction involved.

Solution 40

(a) SO2 is acidic in nature. When dissolved in water, it produces sulphurous acid.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b) Na2O is basic in nature. When dissolved in water, it forms an alkali called sodium hydroxide.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 41

(a)What type of oxides are formed when non-metals react with oxygen? Explain with an example.

(b)What type of oxides are formed when metals combine with oxygen? Explain with the help of an example.

Solution 41

(a) When non-metals react with oxygen, they form acidic oxides or neutral oxides.

Example: Carbon reacts with oxygen to form an acidic oxide called carbon dioxide. Hydrogen reacts with oxygen to form neutral oxide called water.

(b) When metals combine with oxygen, they form basic oxides.

Example: Sodium reacts with oxygen to form a basic oxide called sodium oxide.

Question 42

(a)Explain why, metals usually do not liberate hydrogen gas with dilute nitric acid.

(b)Name two metals which can, however, liberate hydrogen gas from very dilute nitric acid.

Solution 42

(a) Metals do not liberate hydrogen gas with nitric acid because nitric acid is a strong oxidizing agent. So, as soon as hydrogen gas is formed in the reaction between a metal and dilute nitric acid, the nitric acid oxidises this hydrogen to water.

(b) Magnesium and manganese.

Question 43

(a)How do metals react with hydrogen? Explain with an example.

(b)How do non-metals react with hydrogen? Explain with an example.

Solution 43

(a) Most of the metals do not react with hydrogen. Only a few reactive metals react with hydrogen to form metal hydrides. For example: When hydrogen gas is passed over heated sodium, then sodium hydride is formed.

(b) Non-metals react with hydrogen to form covalent hydrides. For example: Sulphur combines with hydrogen to form hydrogen sulphide.

Question 44

(a)What happens when calcium reacts with chlorine? Write an equation for the reaction which takes place.

(b)What happens when magnesium reacts with very dilute nitric acid? Write an equation for the reaction involved.

Solution 44

(a) Calcium reacts vigorously with chlorine to form an ionic chloride called calcium chloride. 

 

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b) Magnesium reacts with very dilute nitric acid to form magnesium nitrate and hydrogen gas.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 45

(a) Arrange the following metals in order of their chemical reactivity, placing the most reactive metal first:

Magnesium, Copper, Iron, Sodium, Zinc, Lead, Calcium.

(b) What happens when a rod of zinc metal is dipped into a solution of copper sulphate? Give chemical equation of the reaction involved.

Solution 45

(a) Sodium > Calcium > Magnesium > Zinc > Iron > Lead > Copper

(b) When a strip of zinc metal is put in copper sulphate solution, then the blue colour of copper sulphate solution fades gradually and red brown coating of copper is deposited on the zinc strip.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Chapter 3 - Metals and Non-metals Exercise 134

Question 46

A copper plate was dipped in AgNO3 solution. After certain time, silver from the solution was deposited on the copper plate. State the reason why it happened. Give the chemical equation of the reaction involved.

Solution 46

Silver gets deposited on the copper plate because copper is more reactive than silver and hence displaces silver from silver nitrate solution.
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 47

State five uses of metals and five of non-metals.

Solution 47

Uses of metals:

(i) Lead metal is used in making car batteries.

(ii) Zinc is used for galvanizing iron to protect it from rusting.

(iii) Iron, copper and aluminium are used to make utensils.

(iv) Copper and aluminium metals are used to make electrical wires.

(v) Aluminium is used to make aluminium foil for packaging materials.

Uses of non-metals:

(i) Hydrogen is used in the hydrogenation of vegetable oils.

(ii) Carbon is used to make electrodes of electrolytic cells and dry cells.

(iii) Nitrogen is used in the manufacture of ammonia, nitric acid and fertilizers.

(iv) Sulphur is used for producing sulphuric acid.

(v) Liquid hydrogen is used as rocket fuel.

Question 48

State one use of each of the following metals:

Copper, Aluminium, Iron, Silver, Gold, Mercury

Solution 48

(i) Copper - Copper is used to make wires to carry electric current.

(ii) Aluminium - Aluminium foils are used in packaging of food materials.

(iii) Iron - Iron is used to make utensils.

(iv) Silver - Silver is used to make jewellery.

(v) Gold - Gold is used to make jewellery.

(vi) Mercury - Mercury is used in thermometers.

Question 49

(a)State one use of each of the following non-metals:

Hydrogen, carbon (as Graphite), Nitrogen, Sulphur

(b)Name the metal which is used in making thermometers.

Solution 49

(a) (i) Hydrogen - Hydrogen is used in the hydrogenation of vegetable oils.

     (ii) Carbon is used to make electrodes of electrolytic cells and dry cells.

     (iii) Nitrogen is used in the manufacture of ammonia, nitric acid and fertilizers.

     (iv) Sulphur is used in making sulphuric acid.

(b) Mercury

Question 50

(a)Why does aluminium not react with water under ordinary conditions?

(b)Name two metals which can displace hydrogen from dilute acids.

(c)Name two metals which cannot displace hydrogen from dilute acids.

Solution 50

(a) Aluminium metal does not react with water under ordinary conditions because of the presence of a thin layer of aluminium oxide on its surface.

(b) Sodium and magnesium.

(c) Copper and silver.

Question 51

(a)Why is sodium kept immersed in kerosene oil?

(b)Why is white phosphorus kept immersed under water?

(c)Can we keep sodium immersed under water? Why?

Solution 51

(a) Sodium is a very reactive metal so it reacts vigorously with the oxygen of air and catches fire. It is kept immersed in kerosene oil to protect it from the action of oxygen, moisture and carbon dioxide of air and to prevent accidental fires.

(b) White phosphorus is kept immersed in water because it reacts spontaneously with oxygen of air to form  phosphorus pentoxide but does not react with water.

(c) No, because sodium reacts vigorously with water to form sodium hydroxide and hydrogen.

Question 52

(a)Describe the reaction of potassium with water. Write the equation of the reaction involved.

(b)Write an equation of the reaction of iron with steam. Indicate the physical states of all the reactants and products.

(c)Which gas is produced when dilute hydrochloric acid is added to a reactive metal?

Solution 52

(a) Potassium reacts violently with cold water to form potassium hydroxide and hydrogen gas.

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b) Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(c) Hydrogen.

Question 53

(a)Give one example, with equation, of the displacement of hydrogen by a metal from an acid.

(b)Name two metals (other than zinc and iron) which can displace hydrogen from dilute hydrochloric acid?

Solution 53

(a) Magnesium reacts with very dilute nitric acid to form magnesium nitrate and hydrogen gas.
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b) Magnesium and aluminium.

Question 54

What is the action of water on (a) sodium (b) magnesium and (c) aluminium? Write equations of the chemical reactions involved.

Solution 54

(a) Sodium reacts vigorously with cold water forming sodium hydroxide and hydrogen gas.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b) Magnesium reacts with hot water to form magnesium hydroxide and hydrogen.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(c) Aluminium reacts with steam to form aluminium oxide and hydrogen gas.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 55

You are given samples of three metals- sodium, magnesium and copper. Suggest any two activities to arrange them in order of their decreasing reactivities.

Solution 55

(i) When sodium, magnesium and copper are left in air, sodium reacts vigorously with oxygen to form sodium oxide, magnesium reacts with oxygen to form magnesium oxide only on heating, whereas copper does not burn in air even on strong heating. It reacts only on prolonged heating. This shows that sodium is most reactive, then magnesium and copper is the least reactive among the three.

(ii) Sodium reacts vigorously with cold water to form sodium hydroxide and hydrogen, magnesium does not react with cold water but reacts with hot water to form magnesium hydroxide and hydrogen but copper does not react even with steam. This shows that sodium is highly reactive; magnesium is less reactive than sodium and copper is the least reactive among the three.

Question 56

(a)Write one reaction in which aluminium oxide behaves as a basic oxide and another in which it behaves as an acidic oxide.

(b)What special name is given to substances like aluminium oxide.

(c)Name another metal oxide which behaves like aluminium oxide.

Solution 56

(a)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

In this reaction, aluminium oxide behaves as a basic oxide because it reacts with an acid to form salt and water.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

In this reaction, aluminium oxide behaves as an acidic oxide because it reacts with a base to form salt and water.

(b) Amphoteric oxides.

(c) Zinc oxide.

Question 57

(a)What happens when calcium reacts with water? Write the chemical equations of the reaction of calcium with water.

(b)Write the chemical equation of the reaction which takes place when iron reacts with dilute sulphuric acid. What happens when the gas produced is ignited with a burning matchstick?

Solution 57

(a) Calcium reacts with cold water to form calcium hydroxide and hydrogen gas.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b) When iron reacts with dilute sulphuric acid, it forms iron sulphate and hydrogen gas.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

When hydrogen gas is ignited with a burning matchstick, it produces a 'pop' sound.

Question 58

You are given a dry cell, a torch bulb with holder, wires and crocodile clips. How would you use them to distinguish between samples of metals and non-metals?

Solution 58

We would create an apparatus using dry cell, a torch bulb fitted in a holder and some connecting wires with crocodile clips and connect them to make an electric circuit. Then insert a piece of sulphur between the crocodile clips and the bulb does not light up at all. This means that sulphur does not allow the electric current to pass through it. Now insert a piece of copper between the crocodile clips and the bulb will light up. This observation shows that non metals (ex- sulphur) do not conduct electricity and metals (ex- copper)  conduct electricity.

Question 59

State any five physical properties of metals and five physical properties of non-metals.

Solution 59

Properties of metals:

(i) Metals are malleable i.e. they can be beaten into thin sheets with a hammer.

(ii) Metals are ductile i.e. they can be drawn into thin wires.

(iii) Metals are good conductors of heat and electricity.

(iv) Metals are lustrous.

(v) Metals are generally hard.

Properties of non-metals:

(i) Non-metals are non-malleable i.e. they cannot be beaten into thin sheets with a hammer.

(ii) Non-metals are non-ductile i.e. they cannot be drawn into thin wires.

(iii) Non-metals are bad conductors of heat and electricity.

(iv) Non-metals are non-lustrous.

(v) Non-metals are generally soft.

Question 60

(a)Name two physical properties each of sodium and carbon in which their behaviour is not as expected from their classification as metal and non-metal respectively.

(b)Name two metals whose melting points are so low that they melt when held in the hand.

Solution 60

(a) Sodium metal: Soft, low melting point

     Carbon non-metal: graphite conducts electricity; diamond has a very high melting point.

(b) Gallium and cesium.

Question 61

Metals are said to be shiny. Why do metals generally appear to be dull? How can their brightness be restored?

Solution 61

Metals lose their shine or brightness on keeping in air for a long time and acquire a dull appearence due to the formation of a thin layer of oxide, carbonate or sulphide on their surface by the slow action of various gases present in air.

Brightness of metals can be restored by rubbing the dull surface of the metal object with a sand paper, then the outer corroded layer is removed and the metal object becomes shiny and bright once again.

Question 62

(a) What are metals? Name five metals.

(b) Name a metal which is so soft that it can be cut with a knife.

(c) Name the metal which is the best conductor of heat and electricity.

(d) What happens when a metal reacts with dilute hydrochloric acid? Explain with the help of an example.

(e) Write the equations for the reactions of:

(i) Magnesium with dilute hydrochloric acid

(ii) Aluminium with dilute hydrochloric acid

(iii) Zinc with dilute hydrochloric acid

(iv) Iron with dilute hydrochloric acid

Name the products formed in each case. Also indicate the physical states of all the substances involved.

Solution 62

(a) Metals are the elements that conduct heat and electricity, and are malleable and ductile.

Example: Iron, aluminium, copper, gold and silver.

(b) Sodium

(c) Silver

(d) When a metal reacts with dilute hydrochloric acid, it forms metal chloride and hydrogen gas.

Example: Magnesium reacts rapidly with dilute hydrochloric acid to form magnesium chloride and hydrogen.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(e) (i)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

The products formed are magnesium chloride and hydrogen.

(ii)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

The products formed are aluminium chloride and hydrogen.

(iii)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

The products formed are zinc chloride and hydrogen.

(iv)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

The products formed are iron chloride and hydrogen.

Chapter 3 - Metals and Non-metals Exercise 135

Question 63

(a) Define non-metals. Give five examples of non-metals.

(b) Name a non-metal which conducts electricity.

(c) Name a non-metal having lustre (shining surface).

(d) Name a non-metal which is extremely hard.

(e) How do non-metals react with oxygen? Explain with an example. Give equation of the reaction involved. What is the nature of the product formed ? How will you demonstrate it?

Solution 63

(a) Non-metals are the elements that do not conduct heat and electricity and are neither malleable nor ductile.

Example: Carbon, sulphur, phosphorus, silicon and oxygen.

(b) Carbon.

(c) Iodine.

(d) Carbon (Diamond).

(e) Non-metals react with oxygen to form acidic oxides or neutral oxides. Carbon burns in air to form carbon dioxide.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

The nature of the product formed is acidic. When carbon dioxide dissolves in water, it forms carbonic acid. It turns blue litmus to red which shows it is acidic in nature.

Question 64

(a) What is meant by the reactivity series of metals? Arrange the following metals in an increasing order of their reactivities towards water:

Zinc, Iron, Magnesium, Sodium

(b) Hydrogen is not a metal but still it has been assigned a place in the reactivity series of metals. Why ?

(c) Name one metal more reactive and another less reactive than hydrogen.

(d) Name one metal which displaces copper from copper sulphate solution and one which does not.

(e) Name one metal which displaces silver from silver nitrate solution and one which does not.

Solution 64

(a) The arrangement of metals in a vertical column in the order of decreasing reactivities is called reactivity series.

Increasing order of reactivity: Iron < zinc < magnesium < sodium

(b) Though hydrogen is not a metal but it has been placed in the reactivity series of metals due to the fact that like metals, hydrogen also loses electrons and forms positive ions.

(c) Lead is more reactive than hydrogen and copper is less reactive than hydrogen.

(d) Zinc displaces copper from copper sulphate solution and mercury does not displace copper from copper sulphate solution.

(e) Copper displaces silver from silver nitrate solution and gold does not.

Question 65

(a) State any three differences between the physical properties of metals and non-metals.

(b) Differentiate between metals and non-metals on the basis of their chemical properties.

(c) State three reasons (of which at least one must be chemical) for believing that sodium is a metal.

(d) State three reasons (of which at least one must be chemical) for believing that sulphur is a non-metal.

(e) Which non-metal has been placed in the reactivity series of metals?

Solution 65

(a) Difference between metals and non-metals:

Metals

Non-metals

(i) Metals are malleable i.e. they can be beaten into thin sheets with a hammer.

 

(ii) Metals are ductile i.e. they can be drawn into thin wires.

(iii) Metals are good conductors of heat and electricity.

 

(i) Non-metals are non-malleable i.e. they cannot be beaten into thin sheets with a hammer.

(ii) Non-metals are non-ductile i.e. they cannot be drawn into thin wires.

(iii) Non-metals are bad conductors of heat and electricity.

 

 

(b) Difference between metals and non-metals:

Metals

Non-metals

(i) Metals form basic oxides.

(ii) Metals displace hydrogen from water

(iii) Metals displace hydrogen from dilute acids.

(i) Non-metals form acidic or neutral oxides.

  (ii) Non-metals do not react with water.

(iii) Non-metals do not react with dilute acids.

 

(c) Sodium is a solid, it conducts electricity and forms basic oxides.

(d) Sulphur is a non-metal as it is brittle, non-ductile, non-conductor of electricity and forms acidic oxides.

(e) Hydrogen.

Chapter 3 - Metals and Non-metals Exercise 136

Question 89

An element E forms an oxide E2O. An aqueous solution of E2O turns red litmus paper blue.

(a) What is the nature of the oxide E2O?

(b) State whether element E is a metal or a non-metal.

(c) Give one example of an element like E.

Solution 89

(a) Basic oxide.

(b) Metal.

(c) Sodium, Na.

Question 90

Metal A burns in air, on heating, to form an oxide A2O3 whereas another metal B bums in air only on strong heating to form an oxide BO. The two oxides A2O3 and BO can react with hydrochloric acid as well as sodium hydroxide solution to form the corresponding salts and water.

(a) What is the nature of oxide A2O3?

(b) What is the nature of oxide BO?

(c) Name one metal like A.

(d) Name one metal like B.

 

Solution 90

(a) Amphoteric oxide.

(b) Amphoteric oxide.

(c) Aluminium, Al.

(d) Zinc, Zn.

Question 91

An element X forms two oxides XO and XO2. The oxide XO has no action on litmus solution but oxide XO2 turns litmus solution red.

(a) What is the nature of oxide XO?

(b) What is the nature of oxide XO2?

(c) Would you call element X a metal or a non-metal? Give reason for your choice.

(d) Can you give an example of element like X?

Solution 91

(a) Neutral oxide.

(b) Acidic oxide.

(c)  X is non-metal because non-metals form acidic and basic oxide.

(d) Carbon, C.

Question 92

State and explain the reactions, if any, of the following metals with a solution of copper sulphate:

(a) Gold     (b) Copper   (c) Zinc     (d) Mercury

 

Solution 92

(a) No displacement reaction will take place because gold is less reactive than copper.

(b) No reaction will take place between copper and copper sulphate solution; there is no reaction possible.

(c) Zinc displaces copper from copper sulphate solution to form zinc sulphate solution and copper metal because zinc is more reactive than copper.

(d) No displacement reaction will take place because mercury is less reactive than copper.

Question 93

(a) Give the names and formulae of one metal chloride and one non-metal chloride.

(b) State an important property in which these metal chloride and non-metal chloride differ.

(c) Why do they differ in this property?

Solution 93

(a) Metal chloride: Sodium chloride, NaCl

     Non-metal chloride: Carbon tetrachloride, CCl4

(b) Sodium chloride solution conducts electricity whereas carbon tetrachloride does not conduct electricity.

(c) Sodium chloride is an ionic compound whereas carbon tetrachloride is a covalent compound.

Chapter 3 - Metals and Non-metals Exercise 137

Question 94

In a solution of lead acetate, a strip of metal M was dipped. After some time, lead from the solution was deposited on the metal strip. Which metal is more reactive, M or lead?

 

Solution 94

M is more reactive than lead since it is able to displace lead from lead acetate solution.

Question 95

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

On the basis of the above reactions, indicate which is most reactive and which is least reactive metal out of zinc, copper and iron.

Solution 95

Zinc is most reactive and copper is least reactive out of the three since iron displaced copper from its solution and zinc displaced iron from its solution.

Question 96

Which of the following reactions will not occur? Why not?

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Solution 96

Reaction (a) will not occur because Cu is less reactive than Mg

Reaction (c) will also not occur because Fe is less reactive than Mg.

Question 97

In nature, metal A is found in a free state while metal B is found in the form of its compounds. Which of these two will be nearer to the top of the activity series of metals?

 

Solution 97

Metal B will be nearer to the top of the activity series since it is highly reactive and is hence found in the form of its compounds and not in free state.

Question 98

If A, B, C, D, E, F, G, H, I, J and K represent metals in the decreasing order of their reactivity, which one of them is most likely to occur in a free state in nature ?

 

Solution 98

K being the lowest in the reactivity series is least reactive and is most likely to occur in a free state in nature.

Question 99

(a) Name a metal for each case:

(i) It does not react with cold as well as hot water but reacts with steam.

(ii) It does not react with any physical state of water.

(b) When calcium metal is added to water, the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?

Solution 99

(a) (i) Iron (ii) Gold

(b) More heat is evolved during the reaction of sodium metal with water due to which the hydrogen gas formed catches fire. On the other hand, less heat is evolved during the reaction of calcium metal with water which cannot make the hydrogen gas burn.

Question 100

A zinc plate was kept in a glass container having CuSO4 solution. On examining it was found that the blue colour of the solution is getting lighter and lighter. After a few days, when the zinc plate was taken out of the solution, a number of small holes were noticed in it. State the reason and give chemical equation of the reaction involved.

 

Solution 100

Zinc metal is more reactive than copper. Some of the zinc metal of zinc plate dissolves and displaces copper from copper sulphate solution. This dissolving of zinc metal forms tiny holes in zinc plate. Blue colour of copper sulphate solution gets lighter and lighter due to the formation of colourless zinc sulphate solution.

Chapter 3 - Metals and Non-metals Exercise 167

Question 1

What is the name of the chemical bond formed:

(a)By the sharing of electrons between two atoms?

(b)By the transfer of electrons from one atom to another?

Solution 1

(a) Covalent bond.

(b) Ionic bond.

Question 2

Name a carbon containing molecule which has two double bonds.

Solution 2

Carbon dioxide, CO2

Question 3

What would be the electron-dot structure of carbon dioxide which has the formula CO2?

Solution 3


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 4

What type of chemical bond is formed between:

(a)Potassium and bromine?

(b)Carbon and bromine?

Solution 4

(a) Ionic bond.

(b) Covalent bond.

Question 5

(a) What do we call those particles which have more or less electrons than the normal atoms?

(b) What do we call those particles which have more electrons than the normal atoms?

(c) What do we call those particles which have less electrons than the normal atoms?

Solution 5

(a) Ions

(b) Anions

(c) Cations

Question 6

(a) The atomic number of sodium is 11. What is the number of electrons in Na+?

(b) The atomic number of chlorine is 17. What is the number of electrons in Cl-?

Solution 6

(a) No. of electrons in Na+= 10

(b) No. of electrons in Cl- = 18

Question 7

The atomic number of an element X is 8 and that of element Y is 12. Write down the symbols of the ions you would expect to be formed from their atoms.

Solution 7

X will form X2-

Y will form Y2+

Question 8

(a)Write down the electronic configuration of (i) magnesium atom, and (ii) magnesium ion. (At. No. of Mg = 12)

(b)Write down the electronic configuration of (i) sulphur atom, and (ii) sulphide ion, (At. No. of S = 16)

Solution 8

(a) (i) E.C of Mg =  2, 8, 2 (ii) E.C of Mg2+ = 2, 8

(b) (i) E.C of S = 2, 8, 6 (ii) E.C of S2- = 2, 8, 8

Question 9

What type of chemical bonds are present in a solid compound which has a high melting point, does not conduct electricity in the solid state but becomes a good conductor in the molten state?

Solution 9

Ionic bonds.

Question 10

State whether the following statement is true or false:

The aqueous solution of an ionic compound conducts electricity because there are plenty of free electrons in the solution.

Solution 10

False (It should be 'ions' in place of 'electrons').

Question 11

What type of bonds are present in hydrogen chloride and oxygen?

Solution 11

Covalent bond

Question 12

Write the electron-dot structures for the following molecules:

(i) NaCl (ii) Cl2

Solution 12

(i)


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(ii)


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 13

What type of bonds are present in water molecule? Draw the electron-dot structure of water (H2O).

Solution 13

Covalent bonds are present in a water molecule.

Electron dot structure of water:

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 14

What type of bonds are present in methane (CH4) and solution chloride (NaCl)?

Solution 14

Methane: Covalent bonds

Sodium chloride: Ionic bonds

Question 15

State one major difference between covalent and ionic bonds and give one example each of covalent and ionic compounds.

Solution 15

Ionic compounds conduct electricity when dissolved in water or melted whereas covalent compounds do not conduct electricity.

Ionic compound - NaCl

Covalent compound - CO2

Question 16

What type of bonds are present in the following molecules? Draw their electron-dot structures.

(i) H2 (ii) CH4 (iii) Cl2 (iv) O2

Solution 16

Covalent bonds are present in the given molecules.

(i) H2


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(ii) CH4


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(iii) Cl2


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(iv) O2


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 17

Which inert gas electron configuration do the Cl atoms in Cl2 molecule resemble? What is this electron configuration?

Solution 17

Argon; E.C = 2,8,8

Question 18

Which of the following compounds are ionic and which are covalent?

Urea, Cane sugar, Hydrogen chloride, Sodium chloride, Ammonium chloride, Carbon tetrachloride, Ammonia, alcohol, Magnesium chloride.

Solution 18

Ionic compounds: Sodium chloride, Ammonium chloride, Magnesium chloride.

Covalent compounds: Urea, Cane sugar, Hydrogen chloride, Carbon tetrachloride, Ammonia, Alcohol.

Question 19

Give one example each of the following:

(i)A molecule containing a single covalent bond

(ii)A molecule containing a double covalent bond

(iii)A molecule containing a triple covalent bond

(iv)A compound containing an ionic bond

Solution 19

(i) Hydrogen

(ii) Oxygen

(iii) Nitrogen

(iv) Sodium chloride

Chapter 3 - Metals and Non-metals Exercise 168

Question 20

Fill in the blanks in the following sentences:

(i)Two atoms of the same element combine to form a molecule. The bond between them is known as _____ bond.

(ii)Two chlorine atoms combine to form a molecule. The bond between them is known as  _____.

(iii)In forming oxygen molecule, _____ electrons are shared by each atom of oxygen.

(iv)In forming N2 molecule, _____ electrons are shared by each atom of nitrogen.

(v)The number of single covalent bonds in C2H2 molecule are _____.

(vi)Melting points and boiling points of ionic compounds are generally  _____ than those of covalent compounds.

Solution 20

(i) Covalent

(ii) Covalent

(iii) Two

(iv) Three

(v) Two

(vi) Higher

Question 21

(a)What is a covalent bond? What type of bond exists in (i) CCl4, and (ii) CaCl2?

(b)What is an ionic bond? What type of bond is present in oxygen molecule?

Solution 21

(a) The chemical bond formed by the sharing of electrons between two atoms is known as a covalent bond.

(i) Covalent bonds (ii) Ionic bonds

(b) The chemical bond formed by the transfer of electrons from one atom to another is known as an ionic bond.

 Covalent bond is present in an oxygen molecule.

Question 22

(a)What is an ion? Explain with examples.

(b)What is the nature of charge on (i) a cation, and (ii) an anion?

(c)Name the cation and anion present in MgCl2. Also write their symbols.

Solution 22

(a) An ion is an electrically charged atom (or group of atoms). Example: Sodium ion, Na+, magnesium ion, Mg2+.

(b) (i) Positive charge (ii) Negative charge

(c)  Cation: Magnesium ion, Mg2+

      Anion: Chloride ions, 2Cl-

Question 23

(a)What type of chemical bond is present in chlorine molecule? Explain your answer.

(b)Explain the formation of a chlorine molecule on the basis of electron theory of valency.

Solution 23

(a) Covalent bond; Because whenever two atoms of the same element combine to form a molecule, a covalent bond is formed.

(b) The atomic number of chlorine is 17, so its electronic configuration is 2,8,7. Chlorine atom has 7 electrons in its outermost shell and needs 1 more electron to complete its octet and become stable. It gets this electron by sharing with another chlorine atom. So, two chlorine atoms share one electron each to form a chlorine molecule. Because the two chlorine atoms share electrons, there is a strong force of attraction between them which holds them together. This force is called covalent bond. Now, each chlorine atom in the chlorine molecule has the electronic configuration 2,8,8 resembling its nearest inert gas argon. Since the chlorine atoms in a chlorine molecule have inert gas electron arrangements, therefore, a chlorine molecule is more stable than two separate chlorine atoms.

Question 24

(a) Giving one example each, state what are (i) ionic compounds, and (ii) covalent compounds.

(b) Compare the properties of ionic compounds and covalent compounds.

Solution 24

(a) (i) The compounds containing ionic bonds are known as ionic compounds. They are formed by the transfer of electrons from one atom to another.

Example: Sodium chloride, NaCl.

(ii) The compounds containing covalent bonds are known as covalent compounds. They are formed by the sharing of electrons between atoms. Example: Methane, CH4.

(b)

Ionic compounds

Covalent compounds

(i) Ionic compounds are usually crystalline solids.

(ii) Ionic compounds have high melting and boiling points.

(iii) Ionic compounds are usually soluble in water.

(i) Covalent compounds are usually liquids or gases.

(ii) Covalent compounds have low melting and boiling points.

(iii) Covalent compounds are usually insoluble in water.

Question 25

Explain why:

(a)Covalent compounds have generally low melting points.

(b)Ionic compounds have generally high melting points.

Solution 25

(a) Covalent compounds have generally low melting points because they are made up of electrically neutral molecules. So, the force of attraction between the molecules of a covalent compound is very weak. Hence, only a small amount of heat energy is required to break these weak molecular forces.

(b) Ionic compounds are made of up of positive and negative ions. There is a strong force of attraction between the oppositely charged ions, so a lot of heat energy is required to break this force of attraction and melt or boil the ionic compound. Due to this, ionic compounds have high melting points.

Question 26

(a)Give two general properties of ionic compounds and two those of covalent compounds.

(b)State one test by which sodium chloride can be distinguished from sugar.

Solution 26

(a) Ionic compounds:

(i) They have high melting and boiling points.

(ii) They are usually soluble in water.

     Covalent compounds:

(i) They have low melting and boiling points.

(ii) They are usually insoluble in water.

(b) An aqueous solution of sodium chloride conducts electricity but a sugar solution does not conduct electricity.

Question 27

(a) Explain why, ionic compounds conduct electricity in solution whereas covalent compounds do not conduct electricity.

(b) Which of the following will conduct electricity and which not?

      MgCl2, CCl4, NaCl, CS2, Na2S

Solution 27

(a) Ionic compounds conduct electricity in solution because they are made up of electrically charged ions but covalent compounds are made up of electrically neutral molecules so they do not conduct electricity.

(b) Conduct electricity: MgCl2, NaCl, Na2S (Ionic compounds)

      Do not conduct electricity: CCl4, CS2 (Covalent compounds).

Question 28

(a) Name one ionic compound containing chlorine and one covalent compound containing chlorine.

(b) How will you find out which of the water soluble compound A or B is ionic?

Solution 28

(a) Ionic compound: Sodium chloride, NaCl.

     Covalent compound: Carbon tetrachloride, CCl4

(b) Out of A and B, the compound whose aqueous solution conducts electricity will be an ionic compound.

Question 29

Explain why, a solution of cane sugar does not conduct electricity but a solution of common salt is a good conductor of electricity.

Solution 29

Common salt is an ionic compound containing ionic bonds whereas cane sugar is a covalent compound containing covalent bonds. Since, ionic compounds conduct electricity and covalent compounds do not, hence common salt is a good conductor of electricity and cane sugar is a non-conductor of electricity.

Question 30

Give the formulae of the compounds that would be formed by the combination of the following pairs of elements:

(a) Mg and N2

(b) Li and O2

(c) Al and Cl2

(d) K and H

Solution 30

(a) Mg3N2

(b) Li2O

(c) AlCl3

(d) KH

Question 31

(a)What are noble gases? What is the characteristic of the electronic configuration of noble gases?

(b)What is the cause of chemical bonding (or chemical combination) of atoms of elements?

Solution 31

(a) There are some elements in group 18 of the periodic table which do not combine with other elements. These elements are helium, neon, argon, krypton, xenon and radon. They are known as noble gases or inert gases because they are unreactive.

If we look at the electronic configuration of noble gases, we would notice that except helium, all other inert gases have 8 electrons (helium has 2) in their outermost shells. This is considered to be the most stable arrangement of electrons.

(b) Atoms form chemical bonds to achieve stability by acquiring the inert gas electron configuration.

Question 32

(i)Write electron-dot structures for magnesium and oxygen.

(ii)Show the formation of MgO by the transfer of electrons.

(iii)What are the ions present in this compound?

Solution 32

(i) Magnesium


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Oxygen


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(ii) Formation of MgO


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(iii) Both positive and negative ions i.e. Mg2+ and O2- respectively.

Question 33

Draw the electron-dot structure of a hydrogen chloride molecule:

(i) Which inert gas does the H atom in HCl resemble in electron arrangement?

(ii) Which inert gas does the Cl atom in HCl resemble in electron arrangement?

Solution 33


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(i) Helium

(ii) Argon

Question 34

What type of bonding would you expect between the following pairs of elements?

(i) Calcium and Oxygen

(ii) Carbon and Chlorine

(iii) Hydrogen and Chlorine.

Solution 34

(i) Ionic bonding.

(ii) Covalent bonding.

(iii) Covalent bonding.

Chapter 3 - Metals and Non-metals Exercise 169

Question 35

Describe how sodium and chlorine atoms are changed into ions when they react with each other to form sodium chloride, NaCl. What is the name given to this type of bonding?

Solution 35

The atomic number of sodium is 11, so its electronic configuration is 2,8,1. Sodium atom has only 1 electron in its outermost shell. So, the sodium atom donates one electron (to a chlorine atom) and forms a sodium ion, Na+. The atomic number of chlorine is 17, so its electronic configuration is 2,8,7. Chlorine atom has 7 electrons in its outermost shell and needs 1 more electron to achieve the stable 8-electron inert gas configuration. So, a chlorine atom takes one electron (from the sodium atom) and forms a negatively charged chloride ion, Cl- . This type of bonding is called ionic bonding.

Question 36

What is the difference between a cation and an anion? How are they formed? Give the names and symbols of one cation and one anion.

Solution 36

A positively charged ion is known as cation. A cation is formed by the loss of one or more electrons by an atom. For example: sodium loses 1 electron to form a sodium ion, Na+, which is a cation.

A negatively charged ion is known as anion. An anion is formed by the gain of one or more electrons by an atom. For example: A chlorine atom gains (accepts) 1 electron to form a chloride ion, Cl-, which is an anion.

Question 37

Using electron-dot diagrams which show only the outermost shell electrons, show how a molecule of nitrogen, N2, is formed from two nitrogen atoms. What name is given to this type of bonding?

Solution 37

Since nitrogen has 5 electrons in its outermost shell so, to achieve the 8-electron structure of an inert gas, it needs 3 more electrons and hence combines with another nitrogen atom to form a molecule of nitrogen gas.
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

This type of bonding is called covalent bonding.

Question 38

Draw the electron-dot structures of the following compounds and state the type of bonding in each case:

(i) CO2

(ii) MgO

(iii) H2O

(iv) HCl

(v) MgCl2

Solution 38

(i) CO2 - Covalent bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(ii) MgO - Ionic bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(iii) H2O - Covalent bond

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(iv) HCl - Covalent bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(v) MgCl2 - Ionic bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 39

Using electron-dot diagrams which show only the outermost shell electrons, show how a molecule of oxygen, O2, is formed from two oxygen atoms. What is the name given to this type of bonding?

Solution 39

Since an oxygen atom has 6 electrons in its outermost shell so, it needs 2 more electrons to achieve the stable 8-electron inert gas configuration. Hence, it combines with another oxygen atom and forms a molecule of oxygen.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

This type of bonding is called a double covalent bond.

Question 40

Draw the electron-dot structures of the following compounds and state the type of bonding in each case:

(i) KCl

(ii) NH3

(iii) CaO

(iv) N2

(v) CaCl2

Solution 40

(i) KCl - Ionic bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(ii) NH3 - Covalent bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(iii) CaO - Ionic bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(iv) N2 - Covalent bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(v) CaCl2 - Ionic bond


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 41

Explain why, a salt which does not conduct electricity in the solid state becomes a good conductor in molten state.

Solution 41

Although solid ionic compounds are made up of ions but they do not conduct electricity in solid state. This is because in the solid ionic compound, the ions are held together in fixed positions by strong electrostatic forces and cannot move freely. However, when we dissolve the ionic solid in water or melt it, the crystal structure is broken down and ions become free to move and conduct electricity. Thus, an aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.

Question 42

(a) Write down the electronic configuration of (i) sodium atom, and (ii) chlorine atom.

(b) How many electrons are there in the outermost shell of (i) a sodium atom, and (ii) a chlorine atom?

(c) Show the formation of NaCl from sodium and chlorine atoms by the transfer of electron(s).

(d) Why has sodium chloride a high melting point?

(e) Name the anode and the cathode used in the electrolytic refining of impure copper metal.

Solution 42

(a) (i) Sodium - 2, 8, 1 (ii) Chlorine - 2, 8, 7

(b) (i) Sodium = 1 (ii) Chlorine = 7

(c)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) Sodium chloride has a high melting point because it is an ionic compound and these compounds are made of up of positive and negative ions. There is a strong force of attraction between the oppositely charged ions, so, a lot of heat energy is required to break this force of attraction and melt or boil the ionic compound.

(e) Anode: Thick block of impure copper metal; Cathode: Thin strip of pure copper metal.

Question 43

(a) Write the electron arrangement in (i) a magnesium atom, and (ii) an oxygen atom.

(b) How many electrons are there in the valence shell of (i) a magnesium atom, and (ii) an oxygen atom.

(c) Show on a diagram the transfer of electrons between the atoms in the formation of MgO.

(d) Name the solvent in which ionic compounds are generally soluble.

(e) Why are aqueous solutions of ionic compounds able to conduct electricity?

Solution 43

(a) (i) Magnesium - 2, 8, 2 (ii) Oxygen - 2, 6

(b) (i) Magnesium = 2 (ii) Oxygen = 6

(c)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) Water.

(e) An aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.

Question 44

(a) What is the electronic configuration of (i) a sodium atom, and (ii) an oxygen atom?

(b) What is the number of outermost electrons in (i) a sodium atom, and (ii) an oxygen atom?

(c) Show the formation of Na2O by the transfer of electrons between the combining atoms.

(d) Why are ionic compounds usually hard?

(e) How is it that ionic compounds in the solid state do not conduct electricity but they do so when in molten state?

Solution 44

(a) (i) 2,8,1 (ii) 2,6

(b) (i) 1 (ii) 6

(c)


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) Ionic compounds are usually hard because their oppositely charged ions attract one another strongly and form a regular crystal structure.

(e) Although solid ionic compounds are made up of ions but they do not conduct electricity in solid state. This is because in the solid ionic compound the ions are held together in fixed positions by strong electrostatic forces and cannot move freely. However, when we dissolve the ionic solid in water or melt it, the crystal structure is broken down and ions become free to move and conduct electricity. Thus, an aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.

Question 45

(a) Write down the electron arrangement in (i) a magnesium atom, and (ii) a chlorine atom.

(b) How many electrons are there in the valence shell of (i) a magnesium atom, and (ii) a chlorine atom.

(c) Show the formation of magnesium chloride from magnesium and chlorine by the transfer of electrons.

(d) State whether magnesium chloride will conduct electricity or not. Give reason for your answer.

(e) Why are covalent compounds generally poor conductors of electricity?

Solution 45

(a) (i) Magnesium: 2, 8, 2 (ii) Chlorine: 2, 8, 7

(b) (i) 2 (ii) 7

(c)

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) Magnesium chloride will conduct electricity because it is an ionic compound.

(e) Covalent compounds are generally poor conductors of electricity because they do not contain ions.

Chapter 3 - Metals and Non-metals Exercise 171

Question 67

Two non-metals combine with each other by the sharing of electrons to form a compound X.

(a)What type of chemical bond is present in X?

(b)State whether X will have a high melting point or low melting point.

(c)Will it be a good conductor of electricity or not?

(d)Will it dissolve in an organic solvent or not?

Solution 67

(a) Covalent bond

(b) Low melting point

(c) No

(d) Yes

Question 68

A metal combines with a non-metal by the transfer of electrons to form a compound Y.

(i)State the type of bonds in Y.

(ii)What can you say about its melting point and boiling point?

(iii)Will it be a good conductor of electricity?

(iv)Will it dissolve in an organic solvent or not?

Solution 68

(i) Ionic bond

(ii) High melting point and boiling point

(iii) Yes

(iv) No

Question 69

The electronic configuration of three elements X, Y and Z are as follows:

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(a)Which two elements will combine to form an ionic compound?

(b)Which two elements will react to form a covalent compound?

Give reasons for your choice.

Solution 69

(a) Y and Z will form an ionic compound because an ionic bond is formed when one of the atoms can donate electrons to achieve the inert gas configuration, and the other atom needs electrons to achieve the inert gas configuration. Since Y has 7 and Z has 1 electron in their outermost shell, they would form an ionic bond.

(b) X and Y will react to form a covalent compound because a covalent bond is formed when both the reacting atoms need electrons to achieve the inert gas electron arrangement.

Question 70

An element A has 4 valence electrons in its atom whereas element B has only one valence electron in its atom. The compound formed by A and B does not conduct electricity. What is the nature of chemical bond in the compound formed? Give its electron dot structure.

Solution 70

Covalent bond will be formed since covalent compounds are non conductors of electricity.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 71

In the formation of a compound XY2 atom X gives one electron to each Y atom. What is the nature of bond in XY2? Give two properties of XY2.

Solution 71

XY2 has ionic bonds.

(i) XY2 would conduct electricity when dissolved in water.

(ii) XY2 would have high melting and boiling point.

Question 72

An element A has two electrons in the outermost shell of its atom and combines with an element B having seven electrons in the outermost shell, forming the compound AB2. The compound when dissolved in water conducts electric current. Giving reasons, state the nature of chemical bond in the compound.

Solution 72

AB2 forms ionic bonds because an aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.

Question 73

The electronic configuration of two elements A and B are given below:

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(a)What type of chemical bond is formed between the two atoms of A?

(b)What type of chemical bond will be formed between the atoms of A and B?

Solution 73

(a) Covalent bond.

(b) Ionic bond.

Question 74

Four elements A, B, c and D have the following electron arrangements in their atoms:

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(a) What type of bond is formed when element C combines with element D?

(b) Which element is an inert gas?

(c) What will be the formula of the compound between A and C?

Solution 74

(a) Ionic bond will be formed; element C donates its electron to element D.

(b) B is an inert gas; has complete octet configuration.

(c) C2A; element A needs two electrons to complete its octet.

Question 75

An element X of atomic number 12 combines with an element Y of atomic number 17 to form a compound XY2. State the nature of chemical bond in XY2 and show how the electron configurations of X and Y change in the formation of this compound.

Solution 75

XY2 forms ionic bond. The electronic configuration of X changes from 2, 8, 2 to 2, 8, it donates its 2 electrons to two Y atoms. Hence, the electronic configuration of Y changes from 2, 8, 7 to 2, 8, 8 giving the compound XY2.

Question 76

The electronic configurations of three elements A, B and C are as follows:

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(a) Which of these elements is a metal?

(b) Which of these elements are non-metals?

(c) Which two elements will combine to form an ionic bond?

(d) Which two elements will combine to form a covalent bond?

(e) Which element will form an anion of valency 1?

Solution 76

(a) A is a metal

(b) B and C are non-metals

(c) A and B combines to form an ionic bond.

(d) B and C combines to form a covalent bond.

(e) B will form an anion with valency 1 since it needs only 1 electron to complete its octet.

Chapter 3 - Metals and Non-metals Exercise 172

Question 77

The electronic configuration of four particles A, B, C and D are given below:

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Which electronic configuration represents:

(i)Magnesium atom?

(ii)Oxygen atom?

(iii)Sodium ion?

(iv)Chloride ion?

Solution 77

(i) B: Magnesium atom (At. no. = 12)

(ii) C: Oxygen atom (At. no. = 8)

(iii) D: Sodium ion (E.C = 2, 8)

(iv) A: Chloride ion (E.C = 2, 8, 8)

Question 78

The atomic number of an element X is 12.

(a)What must an atom of X do to attain the nearest gas electron configuration?

(b)Which inert gas is nearest to X?

Solution 78

(a) An atom of X loses 2 electrons to attain the nearest gas electron configuration (2,8).

(b) Neon

Question 79

The atomic number of an element Y is 16.

(a)What must an atom of Y do to achieve the nearest inert gas electron arrangement?

(b)Which inert gas is nearest to Y?

Solution 79

(a) An atom of Y accepts 2 electrons to achieve the nearest inert gas electron arrangement (2, 8, 8).

(b) Argon

Question 80

You can buy solid air-freshers in shops. Do you think these substances are ionic or covalent? Why?

Solution 80

Solid air-fresheners are covalent compounds because they are volatile compounds with low melting and boiling points.

Question 81

Give the formulae of the chlorides of the elements X and Y having atomic numbers of 3 and 6 respectively. Will the properties of the two chlorides be similar or different? Explain your answer.

Solution 81

Formula of chloride of element X is XCl 

Formula of chloride of element Y is YCl4 

The properties of two chlorides will be different because XCl is an ionic chloride whereas YCl4 is a covalent chloride.

Chapter 3 - Metals and Non-metals Exercise 191

Question 1

A zinc ore gave CO2 on treatment with a dilute acid. Identify the ore and write its chemical formula.

Solution 1

Calamine, ZnCO3

Question 2

What chemical process is used for obtaining a metal from its oxide?

Solution 2

Reduction.

Question 3

State two ways to prevent the rusting of iron.

Solution 3

Rusting of iron can be prevented:

(i) By painting.

(ii) By applying grease or oil.

Question 4

What is meant by galvanisation ? Why is it done?

Solution 4

The process of depositing a thin layer of zinc metal on iron objects is called galvanisation; It prevents iron from rusting.

Question 5
Name the metal which is used for galvanising iron.
Solution 5

Zinc is used for galvanising iron.

Question 6

Explain why, iron sheets are coated with zinc.

Solution 6

Zinc is a quite reactive metal. The action of air on zinc metal forms a very thin coating of zinc oxide all over it, which is hard and impervious to air and hence prevents the further corrosion of zinc metal as well as the iron below it.

Question 7

Why do we apply paint on iron articles?

Solution 7

Iron objects are painted so that air and moisture can not come in contact with the iron objects and hence no rusting takes place.

Question 8

Give reason for the following :

Carbonate and sulphide ores are usually converted into oxides during the process of extraction of metals.

Solution 8

Carbonate and sulphide ores are usually converted into oxides because it is easier to obtain metals from their oxides (by reduction) than from carbonates or sulphides.

Question 9

Name a reducing agent that may be used to obtain manganese from manganese dioxide.

Solution 9

Aluminium powder is used as the reducing agent for the extraction of manganese from its oxide.

Question 10

Name an alloy of lead and tin.

Solution 10

Solder is an alloy of lead and tin.

Question 11

Give the composition of an alloy called solder. State its one property and one use.

Solution 11

Solder is an alloy of lead (Pb) and tin (Sn). It contains both the elements in 50-50 ratio. It has a low melting point and is used for soldering electrical wires together.

Question 12

What is an amalgam?

Solution 12

An alloy of mercury metal with one or more other metals is known as an amalgam.

Question 13

How many carats is pure gold? Why is pure gold not suitable for making ornaments?

Solution 13

Pure gold is said to be of 24 carats. It is not suitable for making ornaments because it is very soft.

Question 14

Name one method for the refining of metals.

Solution 14

Electrolytic refining.

Question 15

State two conditions for the rusting of iron.

Solution 15

(i) Presence of air (oxygen).

(ii) Presence of water (or moisture).

Question 16

In one method of rust prevention, the iron is not coated with anything. Which is this method?

Solution 16

Rusting of iron can be prevented by alloying iron with chromium and nickel to make stainless steel.

Question 17

Name two alloys of iron. What elements are present in these alloys?

Solution 17

Steel - Iron and carbon.

Stainless steel - Iron, chromium and nickel.

Question 18

Give reason for the following :

Silver, gold and platinum are used to make jewellery.

Solution 18

Silver, gold and platinum are used to make jewellery because all of these metals have a bright shiny surface and are resistant to corrosion.

Question 19

Which metal becomes black in the presence of hydrogen sulphide gas in air?

Solution 19

Silver metal becomes black in the presence of hydrogen sulphide gas in air.

Question 20

Name the gas in air which tarnishes silver articles slowly.

Solution 20

Hydrogen sulphide gas tarnishes silver articles.

Question 21

Silver metal does not combine easily with oxygen but silver jewellery tarnishes after some time. How?

Solution 21

The silver articles combine slowly with the hydrogen sulphide gas present in air to form a black coating of silver sulphide. The tarnishing of the silver objects is due to this silver sulphide coating on the object's surface.

Question 22

Write the composition of the alloy called bronze. Give two uses of bronze.

Solution 22

Bronze is an alloy of copper and tin; 90% copper and 10% tin. It is used for making statues and coins.

Question 23

Why does a new aluminium vessel lose shine so soon after use?

Solution 23

A new aluminium vessel lose shine so soon after use due to the corrosion of aluminium metal when exposed to moist air. This happens because the oxygen of air reacts with aluminium to form a thin, dull layer of aluminium oxide all over the vessel.

Question 24
Why do gold ornaments look new even after several years of use?
Solution 24
Gold ornaments look new even after several years of use because gold does not corrode when exposed to atmosphere. It is a highly unreactive metal which remains unaffected by air, water vapour and other gases in the atmosphere.
Question 25

Name two metals which are highly resistant to corrosion.

Solution 25

Gold and platinum are highly resistant to corrosion.

Question 26

Which property of 'solder' alloy makes it suitable for welding electrical wires?

Solution 26

Low melting point of solder makes it sutaible for welding electrical wires.

Question 27

Explain why, carbon cannot reduce oxides of sodium or magnesium.

Solution 27

Carbon cannot reduce oxides of sodium or magnesium because carbon is less reactive than magnesium or sodium. Carbon, which is a non-metal, is more reactive than zinc and can be placed just above Zn in the reactivity series. Hence, carbon can reduce the oxides of zinc and all other metals below zinc to form metals.

Question 28

Why are the metals like Na, K, Ca and Mg never found in their free state in nature?

Solution 28

The metals like Na, K, Ca and Mg never found in their free state in nature because of the reason that all of these metals are high-up in the reactivity series. And just because they are so reactive, they are never found in nature as free elements.

Question 29

Name one metal each which is extracted by:

(a) reduction with carbon              (b) electrolytic reduction

(c) reduction with aluminium         (d) reduction with heat alone

Solution 29

(a) Zinc

(b) Sodium

(c) Manganese

(d) Mercury

Question 30

Fill in the following blanks with suitable words:

(a) The corrosion of iron is called _______.

(b) _______ and _______ are necessary for the rusting of iron.

(c) The process of depositing a thin layer of zinc on iron articles is called _______.

(d) Tiffin boxes are electroplated with _______ but car bumpers are electroplated with _______ to protect them from rusting.

(e) The corrosion of copper produces a _______ coating of basic copper carbonate on its surface.

(j) Brass is an alloy of copper and _______.

(g) Bronze is an alloy of copper and _______.

(h) The non-metal present in steel is _______.

(i) The alloy in which one of the metals is mercury is called an _______.

(j) The electrical conductivity and melting point of an alloy is _______ than that of pure metals.

(k) The rocky material found with ores is called _______. 
Solution 30

(a) rusting

(b) air; water

(c) galvanisation

(d) tin; chromium

(e) green

(j) zinc

(g) tin

(h) carbon

(i) amalgam

(j) less

(k) gangue

Chapter 3 - Metals and Non-metals Exercise 192

Question 31

How is manganese extracted from manganese dioxide, MnO2? Explain with the help of an equation.

Solution 31

Manganese metal is extracted by the reduction of its oxide with aluminium powder as the reducing agent. Thus, when manganese dioxide is heated with aluminium powder, then manganese metal is formed.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 32

What is a thermite reaction? Explain with the help of an equation. State one use of this reaction.

Solution 32

The reduction of a metal oxide to form metal by using aluminium powder as a reducing agent is called a thermite reaction.

This property of reduction by aluminium is made use of in thermite welding for joining the broken pieces of heavy iron objects like girders etc.

A mixture of Iron (III) oxide and aluminium powder is ignited with a burning magnesium ribbon. Aluminium reduces iron oxide to produce iron metal with the evolution of a lot of heat. Due to this heat, iron metal is produced in the molten state. This molten iron is then poured between the broken iron pieces to weld them (to join them).

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 33

Which one of the methods given in column I is applied for the extraction of each of the metals given in column II:

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Solution 33

Electrolytic reduction: Aluminium and Sodium;

Reduction with carbon : Zinc, Iron and Tin;

Reduction with aluminium: Manganese

Question 34

(a) Give reason why copper is used to make hot water tanks but steel (an alloy of iron) is not.

(b) Explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.

Solution 34

(a) Copper does not corrode easily in the presence of water but steel rusts in the presence of water.

(b) The surface of some metals acquires a dull appearance when exposed to air because of the formation of an oxide layer on the surface of the metal.

Question 35

(a) Why does aluminium not corrode right through?

(b) What is meant by 'anodising' ? Why is it done?

Solution 35

(a) Aluminium does not corrode right through because aluminium is more reactive than iron and it forms a layer of aluminium oxide as soon as it comes in contact with moist air. This aluminium oxide layer is very tough and prevents the aluminium underneath from corroding.

(b) The process of thickening of aluminium oxide layer on the surface of aluminium objects by electrolysis is called anodizing. It is done to provide more protection to the aluminium object from corrosion.

Question 36

(a) Why is an iron grill painted frequently?

(b) Explain why, though aluminium is more reactive than iron, yet there is less corrosion of aluminium when both are exposed to air.

 

Solution 36

(a) An iron grill is painted frequently to prevent its rusting.

(b) There is less corrosion of aluminium than iron when both are exposed to air because aluminium forms a layer of aluminium oxide on its surface as soon as it comes in contact with moist air. This aluminium oxide is very tough and prevents it from corroding right through.

Question 37

(a) Name the method by which aluminium metal is extracted.

(b) Give the name and chemical formula of one ore of copper.

(c) How is zinc extracted from its carbonate ore (calamine)? Explain with equations.

Solution 37

(a) Electrolytic reduction.

(b) Copper glance (Cu2S)

(c) When calamine ore is heated strongly in the absence of air i.e. calcined, it decomposes to form zinc oxide and carbon dioxide.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Then, zinc oxide is heated with carbon and zinc metal is produced.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 38

(a) Name two metals which occur in nature in free state as well as in combined state.

(b) Name one ore of manganese. Which compound of manganese is present in this ore? Also write its chemical formula.

(c) A zinc ore on heating in air forms sulphur dioxide. Describe briefly any two stages involved in the conversion of this concentrated ore into zinc metal.

Solution 38

(a) Copper and Silver occur in nature in free state as well as in combined state.

(b) Pyrolusite; Manganese dioxide; MnO2

(c)

(i) Roasting: When zinc sulphide (zinc blende ore) is strongly heated in air (roasted), it forms zinc oxide and sulphur dioxide.

(ii) Reduction: Zinc oxide obtained is heated with carbon to form zinc metal.

Question 39

How does the method used for extracting a metal from its ore depend on the metal's position in the reactivity series? Explain with examples.

Solution 39

Different methods are used for extracting metals belonging to category of highly reactive metals, moderately reactive metals and less reactive metals. This is because the extraction of a metal from its concentrated ore is essentially a process of reduction of the metal compound present in the ore. For example: Manganese metal is obtained by the reduction of its oxide with aluminium powder and not carbon. This is because carbon is less reactive than manganese. Carbon, which is a non-metal, is more reactive than zinc and it can be placed just above Zn in the reactivity series. Hence, carbon can reduce the oxides of zinc and all other metals below zinc to form metals

Question 40

Explain giving one example, how highly reactive metals (which are high up in the reactivity series) are extracted.

Solution 40

The highly reactive metals are extracted by the electrolytic reduction of their molten chlorides or oxides.

Example: Sodium metal is extracted by the electrolytic reduction of molten sodium chloride. When electric current is passed through molten sodium chloride, it decomposes to form sodium metal and chlorine gas.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 41

Describe with one example, how moderately reactive metals (which are in the middle of reactivity series) are extracted.

Solution 41

The moderately reactive metals are extracted by the reduction of their oxides with carbon, aluminium, sodium or calcium.

Example: When zinc sulphide (zinc blende ore) is strongly heated in air (roasted), it forms zinc oxide and sulphur dioxide. This process is called roasting. Then, zinc oxide is heated with carbon to form zinc metal. This process is termed as reduction.

Question 42

How are the less reactive metals (which are quite low in the reactivity series) extracted? Explain with the help of an example.

Solution 42

The less reactive metals are extracted by the reduction of their oxides by heat alone.

Example: Mercury (II) sulphide ore is roasted in air when mercury (II) oxide is formed. When this mercury (II) oxide is heated to about 300oC, it decomposes to form mercury metal.

Question 43

What is meant by refining of a metal? Name the most widely used method for the refining of impure metals obtained by various reduction processes. Describe this method with the help of a labelled diagram by taking the example of any metal.

 

Solution 43

The process of purifying impure metals is called refining of metals.

Electrolytic refining is the most widely used method for the refining of impure metals obtained by various reduction processes.

In an electrolytic tank, acidified copper sulphate (CuSO4 + dilute H2O4) solution forms the electrolyte. A block of impure copper is made into an anode by connecting the positive terminal of a power supply (battery). A thin strip of highly pure copper metal is the cathode of the cell. The negative terminal of the power supply is connected to it.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

A small electric current is passed through the cell. Atoms from the anode enter the electrolyte. The copper from the anode gets converted into copper sulphide. An equal number of copper atoms from the solution get deposited on the cathode. This is to keep the concentration of the solution constant. Impurities from the anode block either remain in solution or collect below the anode, as they are unable to displace copper from the sulphate solution. The insoluble impurities remain in the electrolyte and are called anode mud.

Copper sulphate solution contains ions of Cu++ and SO4--. The following reactions take place at the anode and cathode when an electric current is passed.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Pure copper is scraped or removed from the cathode. Anode becomes thinner as the electrolysis process proceeds. Some important metals like gold and silver are present in the anode mud. These can be recovered separately.

Question 44

(a) Define the terms (i) mineral (ii) ore, and (iii) gangue.

(b) What is meant by the 'concentration of ore'?

(c) Name one ore of copper (other than cuprite). Which compound of copper is present in this ore? Also, write its chemical formula.

Solution 44

(a) (i) Minerals - The natural materials in which the metals or their compounds are found in earth are called minerals.

(ii) Ores - Those minerals from which the metals can be extracted conveniently and profitably are called ores.

(iii) Gangue - The unwanted impurities like sand, rocky material, earthy particles etc., present in an ore are called gangue.

(b) Before extracting metal from an ore, it is necessary to remove these impurities (gangue) from it. By removing the gangue, we get a concentrated ore containing a much higher percentage of metal. This is called concentration of ore; also known as enrichment of ore.

(c) Ore: Copper glance; Copper (I) sulphide, Cu2S.

Chapter 3 - Metals and Non-metals Exercise 193

Question 45

Explain how, a reduction reaction of aluminium can be used for welding cracked machine parts of iron. Write a chemical equation for the reaction involved.

 

Solution 45

A mixture of Iron (III) oxide and aluminium powder is ignited with a burning magnesium ribbon. Aluminium reduces iron oxide to produce iron metal with the evolution of lot of heat. Due to this heat, iron metal is produced in the molten state. This molten iron is poured between broken iron parts of the machine to weld them (to join them).


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 46

(a) What is corrosion?

(b) Name any two metals which do not corrode easily.

(c) What is the corrosion of iron known as?

(d) Explain why, aluminium is a highly reactive metal, still it is used to make utensils for cooking.

Solution 46

(a) The eating up of metals by the action of air, moisture or a chemical (such as an acid) on their surface is called corrosion.

(b) Gold and Platinum

(c) Rusting

(d) Aluminium begins to corrode quickly when it comes in contact with moist air. The action of moist air on aluminium metal forms a thin layer of aluminium oxide all over the metal. This aluminium oxide is very tough and prevents the metal underneath from further corrosion. Therefore, aluminium is used for making utensils irrespective of its highly reactive property as its corrosion leads to the non-corrosion of the metal in the longer run.

Question 47

What is meant by 'rusting of iron'? With the help of labelled diagrams, describe an activity to find out the conditions under which iron rusts.

Solution 47

When an iron object is left in damp air (or water) for a considerable time, it gets covered with a red-brown flaky substance called rust. This is called rusting of iron.

Experiment to show that rusting of Iron requires both, air and water:

We take three test-tubes and put one clean iron nail in each of the three test-tubes:


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

1. In the first test-tube containing iron nail, we put some anhydrous calcium chloride and close its mouth with a tight cork. Anhydrous calcium chloride absorbs water moisture from the damp air present in the test-tube and make it dry. In this way, the iron nail in the first test-tube is kept in dry air (having no water vapour in it).

2. In the second test-tube containing iron nail, we put boiled distilled water. Boiled water does not contain any dissolved air (or oxygen) in it (this is because the process of boiling removes all the dissolved air from it). A layer of oil is put over boiled water in the test-tube to prevent the outside air from mixing with boiled water. In this way, the iron nail in the second test-tube is kept in air free boiled water.

3. In the third test-tube containing an iron nail, we put unboiled water so that about two-thirds of nail is immersed in water and the rest is above the water, exposed to damp air. In this way, the iron nail in the third test-tube has been placed in air and water together.

The mouth of all three test tubes is closed with a cork and it is kept aside for about one week.

After one week, we observe the iron nails kept in all the three test-tubes, one by one. We find that (i) No rust is seen on the surface of iron nail kept in dry air (water-free air) in the first test-tube. This tells us that rusting of iron does not take place in air alone.

(ii) No rust is seen on the surface of iron nail kept in air-free, boiled water in the second test-tube. This tells us that rusting of iron does not take place in water alone.

(iii) Red-brown rust is seen on the surface of iron nail kept in the presence of both air and water together the third test-tube. This tells us that rusting of iron takes place in the presence of both air and water together.

Question 48

(a) What is an alloy? How is an alloy made?

(b) What elements are present in steel? How are the properties of steel different from those of pure iron?

(c) Give the constituents and one use of brass.

Solution 48

(a) An alloy is a homogeneous mixture of two or more metals (or a metal and small amount of non-metals). An alloy is prepared by mixing the various metals in molten state in required proportions, and then cooling their mixture to the room temperature.

(b) Steel contains iron and carbon.

This alloy of iron (steel) is hard and strong. It also rusts less readily than pure iron.

(c) Brass contains copper and zinc.

Brass is used for making cooking utensils.

Question 49

(a) Name two metals which resist corrosion due to the formation of a thin, hard and impervious layer of oxide on their surface.

(b) Name five methods of preventing rusting of iron.

(c) What are the constituents of stainless steel? What are the special properties of stainless steel?

Solution 49

(a) Aluminium and Zinc resist corrosion due to the formation of a thin, hard and impervious layer of oxide on their surface.

(b) (i) Painting (ii) Applying grease or oil (iii) Galvanisation (iv) Tin and chromium plating (v) Alloying to form stainless steel.

(c) Stainless steel contains iron, chromium and nickel.

Stainless steel does not rust at all and is strong and tough.

Question 50

(a) Name an alloy of copper. State its chemical composition and any one use.

(b) Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as ?

Solution 50

(a) Brass: It contains Copper (Cu) - 80% and Zinc (Zn) - 20%. It is used for making cooking utensils.

(b) When a copper object remains in damp air for a considerable time, then copper reacts slowly with the carbon dioxide and water of air to form a green coating of basic copper carbonate on the surface of the object. The formation of this green coating of basic copper carbonate corrodes it. This process is known as corrosion of copper.

Question 51

(a) How does the painting of an iron object prevent its rusting?

(b) How does the electrical conductivity of copper alloys, brass and bronze, differ from that of pure copper?

(c) What is meant by 22 carat gold? Name the metals which are usually alloyed with gold to make it harder.

Solution 51

(a) When a coat of paint is applied to the surface of an iron object, it prevents air and moisture to come in contact with the object; hence no rusting takes place.

(b) The electrical conductivity of copper alloys like brass and bronze is less than that of pure copper.

(c) It means that 22 parts pure gold is alloyed with 2 parts of either silver or copper for making ornaments; Silver and copper are usually alloyed with gold to make it harder.

Question 52

Explain giving equation, what happens when:

(a) ZnCO3 is heated in the absence of air?

(b) a mixture of Cu2O and Cu2S is heated?

Solution 52

(a) When zinc carbonate is heated strongly in the absence of air, it decomposes to form zinc oxide and carbon dioxide.
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(b) When copper (I) oxide reacts with copper (I) sulphide, it forms copper metal and sulphur dioxide.

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Question 53

(a) For the reduction of a metal oxide, suggest a reducing agent other than carbon.

(b) Explain why, an aqueous solution of sodium chloride is not used for the electrolytic extraction of sodium metal.

Solution 53

(a) Aluminium can be used a reducing agent other than carbon.

(b) We cannot use an aqueous solution of sodium chloride to obtain sodium metal because if we electrolyse an aqueous solution of sodium chloride, then as soon as sodium metal is produced at cathode, it will react with water present in the aqueous solution to form sodium hydroxide. Hence, electrolysis of an aqueous solution of sodium chloride will produce sodium hydroxide and not sodium metal.

Question 54

How are metals refined by the electrolytic process? Describe the electrolytic refining of copper with the help of a neat labelled diagram.

 

Solution 54

For the refining of an impure metal by the process of electrolysis, a thick block of impure metal is made anode (connected to +ve terminal of the battery) and a thin strip of the pure metal is made cathode (connected to -ve terminal of battery). A water soluble salt (of the metal to be refined) is taken as electrolyte. On passing current, impure metal dissolves from the anode and goes into the electrolyte solution. And pure metal from the electrolyte deposits on the cathode.

 

Electrolytic refining of copper: In an electrolytic tank, acidified copper sulphate (CuSO4  + dilute H2O4) solution forms the electrolyte. A block of impure copper is made into an anode by connecting the positive terminal of a power supply (battery). A thin strip of highly pure copper metal is the cathode of the cell. The negative terminal of the power supply is connected to it.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

A small electric current is passed through the cell. Atoms from the anode enter the electrolyte. The copper from the anode gets converted into copper sulphide. An equal number of copper atoms from the solution get deposited on the cathode. This is to keep the concentration of the solution constant. Impurities from the anode block either remain in solution or collect below the anode, as they are unable to displace copper form the sulphate solution. The insoluble impurities remain in the electrolyte and are called anode mud.

Copper sulphate solution contains ions of Cu++ and SO4--. The following reactions take place at the anode and cathode when an electric current is passed.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Pure copper is scraped or removed from the cathode. Anode becomes thinner as the electrolysis process proceeds. Some important metals like gold and silver are present in the anode mud. These can be recovered separately.

Question 55

(a) Name the chemical compound which is electrolysed in molten state to obtain aluminium metal. Which gas is evolved during this process?

(b) Name the chemical compound which is electrolysed in molten state to obtain sodium metal. Which gas is produced in this process ?

(c) Name the gas produced when calamine ore is calcined.

(d) Name the gas evolved when cinnabar ore is roasted.

Solution 55

(a) Aluminium oxide is electrolysed in molten state to obtain aluminium metal. Oxygen gas is evolved during the process.

(b) Sodium chloride is electrolysed in molten state to obtain sodium metal. Chlorine gas is evolved during this process.

(c) Carbon dioxide is produced when calamine ore is calcined.

(d) Sulphur dioxide gas is evolved when cinnabar ore is roasted.

Question 56

(a) Name two metals which are found in nature mainly in the free state (as metallic elements).

(b) Name two metals which are always found in combined state.

(c) What iron compound is present in haematite ore? Also write its chemical formula.

Solution 56

(a) Gold and Platinum are found in nature mainly in the free state.

(b) Sodium and Magnesium are always found in combined state.

(c) Iron (III) oxide; Fe2O3  is present in haematite ore.

Question 57

(a) What is the difference between a mineral and an ore?

(b) Which metal is extracted from cinnabar ore?

(c) Name one ore of sodium. Name the sodium compound present in this ore and write its chemical formula.

(d) How is sodium metal extracted? Explain with the help of equation of the reaction involved.

(e) Name three other metals which are extracted in a manner similar to sodium.

Solution 57

(a) The natural materials in which the metals or their compounds are found in earth are called minerals. Those minerals from which the metals can be extracted conveniently and profitably are called ores.

(b) Mercury.

(c) Rock salt - Sodium chloride, NaCl.

(d) Sodium metal is extracted by the electrolytic reduction of molten sodium chloride. When electric current is passed through molten sodium chloride, it decomposes to form sodium metal and chlorine gas.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(e) Potassium, Calcium and Magnesium.

Question 58

(a) Name the metal which is extracted from haematite ore.

(b) Name one ore of aluminium. Name the aluminium compound present in this ore and write its chemical formula.

(c) How is aluminium metal extracted? Explain with the help of an equation.

(d) Name the electrode at which aluminium metal is produced.

(e) Which gas is produced during the extraction of aluminium? At which electrode is this gas produced?

Solution 58

(a) Iron is extracted from haematite ore.

(b) Bauxite; Aluminium oxide, Al2O3.2H2O

(c) Aluminium metal is extracted by the electrolytic reduction (electrolysis) of molten aluminium oxide. When electric current is passed through molten aluminium oxide, it decomposes to form aluminium metal and oxygen gas.

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) Aluminium metal is produced at Cathode (Negative electrode).

(e) Oxygen gas is produced; at anode (Positive electrode).

Chapter 3 - Metals and Non-metals Exercise 194

Question 59

(a) Which metal is extracted from bauxite ore?

(b) Give the name of one ore of iron. Which iron compound is present in this ore? Write its chemical formula.

(c) Describe the extraction of zinc metal from its sulphide ore (zinc blende). Write equations of the reactions involved.

(d) Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.

(e) Name a common metal which is highly resistant to corrosion.

Solution 59

(a) Aluminium.

(b) Haematite; Iron (III) oxide, Fe2O3

(c) Zinc sulphide (zinc blende ore) is strongly heated in air (roasted), it forms zinc oxide and sulphur dioxide. This process is called roasting.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

Then, zinc oxide is heated with carbon to form zinc metal. This process is termed as reduction.

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) The galvanized iron object remains protected against rusting even if a break occurs in the zinc layer because zinc is more easily oxidised than iron. Hence, the zinc continues to corrode but iron object does not corrode or rust.

(e) Aluminium.

Question 60

(a) Name the metal which is extracted from the ore called 'rock salt'.

(b) Name two ores of zinc. Write the names of the chemical compounds present in them and give their chemical formulae.

(c) Explain how, mercury is extracted from its sulphide are (cinnabar). Give equations of the reactions involved.

(d) In the electrolytic refining of a metal M, what would you take as anode, cathode and electrolyte?

(e) Name any five metals which are purified by electrolytic refining method.

Solution 60

(a) Sodium.

(b) (i) Calamine; Zinc carbonate, ZnCO3

     (ii) Zinc blende; Zinc sulphide, ZnS

(c) Mercury (II) sulphide ore is roasted in air when mercury (II) oxide is formed.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

When this mercury (II) oxide is heated to about 300oC, it decomposes to form mercury metal.


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) Anode - Thick block of impure metal M

     Cathode - Thin strip of pure metal M

     Electrolyte - Water soluble salt (of metal M).

(e)  (i) Copper

      (ii) Zinc

      (iii) Nickel

      (iv) Gold

      (v) Silver

Question 61

(a) Which metal is extracted from calamine ore?

(b) Name one ore of mercury. Which mercury compound is present in this ore? Write its chemical formula.

(c) How is copper extracted from its sulphide ore (copper glance), Cu2S ? Explain with equations of the reactions involved.

(d) What is an alloy? Give two examples of alloys.

(e) How are the properties of an alloy different from those of the constituent elements?

Solution 61

(a) Zinc

(b) Cinnabar; Mercury (II) sulphide, HgS

(c) The concentrated copper (I) sulphide ore (copper glance), Cu2S is roasted in air when a part of copper (I) sulphide is oxidised to copper (I) oxide.

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

When a good amount of copper (I) sulphide has been converted to copper (I) oxide, then the supply of air for roasting is stopped. In the absence of air, copper (I) oxide formed above reacts with remaining copper (I) sulphide to form copper metal and sulphur dioxide.

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) An alloy is a homogeneous mixture of two or more metals (or a metal and small amounts of non-metals).

Steel and Brass are examples of alloys.

(e) (i) Alloys are stronger than the metals from which they are made.

      (ii) Alloys are harder than the constituent metals.

      (iii) Alloys are more resistant to corrosion.

      (iv) Alloys have lower melting points than constituent metals.

      (v) Alloys have lower electrical conductivity than pure metals.

Chapter 3 - Metals and Non-metals Exercise 195

Question 92

An element A which is a part of common salt and kept under kerosene reacts with another element B of atomic number 17 to give a product C. When an aqueous solution of product C is electrolysed, then a compound D is formed and two gases are liberated.

(a) What are A and B?

(b) Identify C and D.

(c) What will be the action of C on litmus solution? Why?

(d) State whether element B is a solid, liquid or gas at room temperature.

(e) Write formula of the compound formed when element B reacts with an element E having atomic number 5.

Solution 92

(a) A is sodium and B is chlorine

(b) C is sodium chloride and D is sodium hydroxide

(c) C will have no effect on litmus solution since it is neutral in nature.

(d) B is a gas at room temperature.

(e) EB3

Question 93

A metal which exists as a liquid at room temperature is obtained by heating its sulphide ore in the presence of air.

(a) Name the metal and write its chemical symbol.

(b) Write the name and formula of the sulphide ore.

(c) Give the equations of chemical reactions involved in the production of metal from its sulphide ore.

(d) Name a common device in which this metal is used.

(e) Can this metal displace copper from copper sulphate solution ? Why ?

Solution 93

 

(a) Mercury, Hg

(b) Cinnabar, HgS

(c)
Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals


Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) Thermometer

(e) No; Because it is less reactive than copper.

Chapter 3 - Metals and Non-metals Exercise 196

Question 94

No chemical reaction takes place when granules of a rusty-brown solid A are mixed with the powder of another solid B. However, when the mixture is heated, a reaction takes place between its components. One of the products C is a metal and settles down in the molten state while the other product D floats over it. It was observed that the reaction is highly exothermic.

(a) What could the solids A and B be?

(b) What are the products C and D most likely to be?

(c) Write the chemical equation for the reaction between A and B leading to the formation of C and D. Mention the physical states of all the reactants and products in this equation and indicate the heat change which takes place.

(d) What is the special name of such a reaction? State one use of such a reaction.

(e) Name any two types of chemical reactions under which the above reaction can be classified.

Solution 94

(a) A is iron (III) oxide and B is aluminium powder.

(b) C is molten iron metal and D is aluminium oxide.

(c)
   

Lakhmir-singh-and-manjit-kaur Solutions Cbse Class 10 Chemistry Chapter - Metals And Non Metals

(d) This reaction is called thermite reaction. It is used for welding of broken pieces of heavy iron objects like railway tracks, etc.

(e) Displacement reactions and oxidation-reduction reactions.

Question 95

In an electrolytic tank, aluminium metal is being extracted by the electrolysis of molten aluminium oxide using carbon electrodes. It is observed that one of the carbon electrodes is gradually burnt away and has to be replaced.

(a) Which carbon electrode (cathode or anode) is burnt away?

(b) Why is this carbon electrode burnt away?

Solution 95

(a) Positively charged carbon electrode (Anode)

(b) This carbon electrode is burnt away because oxygen produced during the electrolysis of molten aluminium oxide reacts gradually with the carbon of carbon anode to form carbon dioxide gas.

Question 96

A metal X which is resistant to corrosion is produced by the electrolysis of its molten oxide whereas another metal Y which is also resistant to corrosion is produced by the reduction of its oxide with carbon. Metal X can be used in powder form in thermite welding whereas metal Y is used in making cathodes of ordinary dry cells.

(a) Name the metals X and Y.

(b) Which of the two metals is more reactive: X or Y ?

(c) Name one ore of metal X. Also write its chemical formula.

(d) Name one ore of metal Y. Also write its chemical formula.

(e) Name one alloy of metal X and one alloy of metal Y.

Solution 96

(a) X is aluminium and Y is zinc.

(b) X is more reactive than Y.

(c) Bauxite; Al2O3.2H2O

(d) Calamine, ZnCO3

(e) Alloy of metal X : Duralumin ; Alloy of metal Y : Brass

Question 97

When an object made of metal A is kept in air for a considerable time, it loses its shine and becomes almost black due to the formation of a layer of substance B. When an object made of another metal C is kept in damp air for a considerable time, it gets covered with a green layer of substance D. Metal A is the best conductor of electricity whereas metal C is the next best conductor of electricity.

(a) What is metal A?

(b) What is metal C?

(c) Name the substance B.

(d) Name the substance D.

(e) What type of chemical can be used to remove the green layer from metal C and clean it? Why?

Solution 97

(a) Silver

(b) Copper

(c) Silver sulphide

(d) Basic copper carbonate

(e) Dilute acid solution; The acid solution dissolves green coloured basic copper carbonate present on the corroded copper object makes it look shiny, red brown again.

Question 98

Four metals P, Q, R and S are all obtained by the reduction of their oxides with carbon. Metal P is used to form a thin layer over the sheets of metal S to prevent its corrosion. Metal Q is used for electroplating tiffin boxes made of metal S whereas metal R is used in making car batteries. Metals Q and R form an alloy called solder. What are metals P, Q, R and S? How have you arrived at this conclusion?

Solution 98

Metal P is zinc; Metal Q is tin; Metal R is lead; Metal S is iron.

Metal P (zinc) is used to form a thin layer on metal S (iron) by the process of galvanisation to prevent its corrosion.

Metal Q (tin) is used for electroplating tiffin boxes made of metal S (iron).

Metal R (lead) is used in making car batteries.

Metals Q (tin) and R (lead) form an alloy called solder.

Question 99

A black metal oxide XO2 is used as a catalyst in the preparation of oxygen gas from potassium chlorate. The oxide XO2 is also used in ordinary dry cells. The metal oxide XO2 cannot be reduced satisfactorily with carbon to form metal X.   

(a) Name the metal X.

(b) Name the metal oxide XO2.

(c) Which reducing agent can be used to reduce XO2 to obtain metal X?

(d) Name another metal which can also be extracted by the reduction of its oxide with the above reducing agent.

Solution 99

(a) Manganese

(b) Manganese dioxide

(c) Aluminium

(d) Chromium

Question 100

Metals X and Y can be recovered from the anode mud left behind after the electrolytic refining of copper metal. The coins made of metal X look new even after several years of use but the coins made of metal Y lose their shine gradually and get blackened soon. When metal X is alloyed with a small amount of metal Y, it becomes hard and hence suitable for making ornaments. What are metals X and Y? Also state the colour of metal X.

Solution 100

Metal X is gold and Metal Y is silver; The colour of metal X (gold) is yellow.