Class 10 FRANK Solutions Chemistry Chapter 7 - Metallurgy
Revise your Chemistry lessons with our Frank Solutions for ICSE Class 10 Chemistry Chapter 7 Metallurgy. Study the definition of chapter-related terms such as flux, ore, slag, alloy, charge etc. Find out how an ore gets concentrated during the froth flotation process. The textbook solutions will also help you learn the concept of refining of metals along with the common refining methods.
Practise TopperLearning’s ICSE Class 10 Chemistry Frank Solutions to understand how to write balanced equations for oxides of carbon, reduction of iron and so on. In addition, use our concept videos, Selina Solutions, online practice tests and other Chemistry resources for board exam preparation.
Metallurgy Exercise 179
(i) Gold and Platinum.
(vii) Iron pyrites.
(ix) Cryolite, aluminium fluoride, Calcium fluoride.
(x) Cathode: inner lining of gas-carbon of the electrolytic cell.
Anode: Thick carbon rods dipping into the fused electrolytes.
(xi) Thermite welding.
(xii) Copper and silver.
(xiii) Aluminium, Iron.
(xiv) platinum and gold
(xv) sodium and potassium
(ii) Nitric acid can be stored in aluminium containers because it do not attack aluminium. It renders aluminium passive due to the formation of an oxide film on surface of aluminum.
(iii) Aluminium oxide cannot be reduced by carbon because it is comparatively high in electrochemical series hence more reactive than carbon.
(iv) A neutral gas other than oxygen is formed at the anode during electrolysis of fused alumina because the oxygen gas formed at the anode oxidizes the carbon of the anode to carbon dioxide.
(v) Extraction of aluminium was very difficult in the beginning because it was very expensive.
(vi) Carbon anodes are used in the electrolytic extraction of aluminium because carbon in the form of graphite is a good conductor of electricity.
(vii) Galvanized metal ions should not be used for storing food as food acids may react with the zinc coating and cause food poisoning.
(ii) Ore: Those minerals from which a metal can be extracted profitably are called ores.
(iii) Gangue: The rocky impurities like (SiO2) present in an ore are called gangue.
(iv) Charge: The mixture of materials fed into a furnace to extract a metal is called charge.
(v) Flux: The substance added to get rid of gangue in the extraction of metal is called flux.
(vi) Slag: The product obtained by the combination of gangue with flux is called slag.
Metallurgy Exercise 180
Hence "All ores are minerals but all minerals are not ores".
(b) Zinc: Zinc blende (ZnS) and Calamine (ZnCO3).
(c) Aluminium:Bauxite (Al2O3) and Cryolite (AlF3.3NaF).
Refining of metals: It is the further purification of metals obtained by reduction process to remove all the impurities.
Depending upon the nature of metal, nature of impurities and purpose for which metal is to be used. The three methods used for refining are:
An alloy is a homogeneous mixture of two or more metals fused together and then solidified.
Alloys are made because they have many salient features:
1. Alloys are stronger and harder than the metals of which they are made.
2. Alloys are more resistant to corrosion.
Amalgam: A mixture or an alloy of mercury with a number of metals or non-metals is known as amalgams. An amalgam may be liquid such as Na/Hg or a solid like Zn/Hg.
Iron does not form amalgam.
Dental amalgam which is a mixture of mercury with a silver tin alloy is used for dental fillings.
(ii) Stainless steel is more useful than steel as it is harder, has high tensile strength, more lustre, more resistance to corrosion and many chemicals.
(iii) Aluminium is extensively used for making aircraft parts because of features like high tensile strength, corrosion resistance light but hard and tough.
(iv) Cold water has no action on aluminium while burning aluminium decomposes steam.
(i) Zinc oxide
Metallurgy Exercise 181
(i) An aqueous solution of sodium chloride is not used for electrolytic reduction of sodium metal because if we electrolyse an aqueous solution of sodium chloride, then as soon as sodium metal is produced at the cathode, it will react with water to form sodium hydroxide. So electrolysis of aqueous sodium chloride solution will produce sodium hydroxide and not sodium metal.
(ii) Reducing agents for the reaction of a metal oxide: Aluminium, carbon monoxide and hydrogen
(b) iron which cannot be easily acted upon by acidsis called as passive iron. Galvanized iron is called passive iron since coating of zinc protects the iron from corrosion as zinc is more electropositive and so would be attacked first.
(a). Cryolite is Na3AlF6 and its chemical name is Sodium aluminium fluoride.
(b). Cryolite is used in the electrolysis of alumina. The function of cryolite is to
(i) Reduce melting point of alumina
(ii) Make molten alumina a good conductor of electricity
(d) Carbon in the form of graphite
Metallurgy Exercise 182
An alloy is a homogeneous mixture of two or more metals fused together and then solidified.
(a) The special property of duralumin is:
Light but hard
Resistant to corrosion
(b) Type metal = Hard
Ore Those minerals from which a metal can be extracted profitably are called ores. For example bauxite ore is used to extract aluminium metal, hematite ore is used to extract iron metal.
(c) form negative ions.
(d) basic oxides.
Metallurgy Exercise 183
(b) Metal would be obtained at cathode.
(c) Graphite, like metals is a good conductor of electricity.
(d) acidic, acidic
Metallurgy Exercise 184
Metallurgy Exercise 185
(ii) A, C E
(b) (i) Sodium hydroxide solution
(b) For brass: Copper and zinc.
(d) Calcium silicate.
(e) Zone of heat absorption.
Metallurgy Exercise 186
(b) Mercury as it is a liquid metal while the rest aresolid.
(b) Bauxite is the chief ore of aluminium.
(b) Molten fluorides of Al, Na and Ba.
(c) Graphite rods.
Metallurgy Exercise 187
(a) Metals are good conductors of electricity.
(b) Metals are malleable and ductile.
(c) Metals form non-polar covalent compounds.
False (Metals form ionic compounds.)
(d) Metals have 1 or 2 or 3 electrons in their valence shell.
(iii) Stainless steel
(i) A metal which is found abundantly in the Earth's crust is aluminium.
(ii) Differences between calcination and roasting:
1. The ore is heated in the
absence of air.
1. The ore is heated in
excess of air.
2. Moisture and organic
impurities are removed, and the ore becomes porous and more reactive.
2. Volatile impurities are
removed as oxides (SO2, P2O5, As2O3), and the ore becomes porous and more reactive.
3. Carbonate and hydrated ores are calcined, and CO2 or water vapour is given off.
ZnCO3 → ZnO + CO2
3. Sulphide ores are roasted, so SO2 is given off.
(iii) Froth flotation process is used for the enrichment of sulphide ore.
(iv) Ore of iron
Ores of aluminium
(v) Constituents of the electrolyte for the extraction of aluminium are pure alumina (Al2O3) cryolite (Na3AlF6) and fluorspar (CaF₂).
(i) Y is the metallic element.
(ii) Metal atoms tend to have a maximum of 3 electrons in the outermost energy level.
(iii) Non-metallic elements tend to form acidic oxides, while metals tend to form basic oxides.
(iv) Non-metallic elements tend to be poor conductors of heat and electricity.
(v) Metals tend to lose electrons and act as reducing agents in their reactions with elements and compounds.
Metallurgy Exercise 188
Extraction of aluminium:
(i) Cryolite (Na3AlF6) is added along with alumina and fluorspar. It lowers the fusion temperature from 2050°C to 950°C and enhances conductivity.
(ii) Al3+ + 3e-→ Al
(iii) It is necessary to renew the anode periodically as it gets oxidised by the oxygen evolved at the anode.
(i) Main components of brass are copper and zinc.
(ii) Main components of duralumin are aluminium, magnesium, copper and manganese.
(iii) Main components of bronze are copper, zinc and tin.
(i) Malleability is the property possessed by metals by which they can be beaten into sheets.
(ii) Cryolite is added to lower the fusion temperature of an electrolytic bath in the extraction of aluminium.
(iii) Zinc blende (sphalerite) is the ore of zinc containing its sulphide.
(a) The main ore used for the extraction of iron is
(b) Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as calcination.
(a) It is a strong reducing agent.
In the extraction of aluminium, the given compounds play the following roles:
(a) Cryolite: It lowers the fusion temperature from 2050°C to 950°C and enhances conductivity.
(b) Sodium hydroxide:
Two roles are played by sodium hydroxide in the extraction of aluminium.
First, finely grinded bauxite (ore of aluminium) is heated under pressure with conc. caustic soda solution (NaOH solution) for 2-8 hours at 140°C to 150°C to produce sodium aluminate. The chemical equation is as follows:
Al2O3.2H2O + 2NaOH → 2NaAlO2+ 3H2O
Second, on diluting sodium aluminate with water and
cooling to 50°C, sodium aluminate is hydrolysed to give
aluminium hydroxide as a precipitate. Here, the impurities
dissolve in sodium hydroxide.
(c) Graphite: Thick rods of graphite are suspended in the fused electrolyte. They act as an anode where oxygen gas is discharged.
(i) In the electrolysis of alumina using the Hall-Héroult process, the electrolyte is covered with powdered coke as it
a. reduces heat loss by radiation
b. prevents the burning of the anode
(ii) Iron sheets are coated with zinc during galvanisation to prevent them from rusting.
Metallurgy Exercise 189
(i) Conc. caustic soda
(iv) At the cathode: Al3++ 3e-→ Al
(v) The anode has to be replaced from time to time as it gets oxidised by oxygen evolved at the anode.
Copper and tin
(iii) Zinc blende
(iv) PbO or CuO
(i) Components of electrolyte: Cryolite and fluorspar
Role played by each electrolyte is given below:
a. Cryolite lowers the fusion temperature from 2050°C to 950°C and enhances conductivity.
b. Fluorspar and cryolite act as a solvent for the electrolytic mixture and increase conductivity.
(ii) Powdered coke is sprinkled over the surface of the electrolytic mixture for the following reasons:
a. To reduce heat loss by radiation
b. To prevent burning of the anode
(i) The process of crushing ores into a fine powder in big crushers and ball mills is known as pulverisation.
(ii) Heating of the ore in the absence of air to a high temperature that is high but insufficient to melt the ore is known as calcination.