FRANK Solutions for Class 10 Chemistry Chapter 6 - Electrolysis
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Chapter 6 - Electrolysis Exercise 145
Chapter 6 - Electrolysis Exercise 146
Choose the correct answer from the options given below:
(i) Which one is weak electrolyte?
(ii) Which among the following cations will discharge with ease at cathode?
(iii) Which among the following anions will discharge with ease at anode?
(iv) In electrolysis of molten lead bromine anode is made up of
(a) Steel rod
(b) Platinum foil
(c) Glass rod
(d) Graphite rod
(v) Electrolysis of acidulated water is used in the production of
(d) Hydrogen and oxygen
(iv) Graphite rod
(v) Hydrogen and oxygen
Chapter 6 - Electrolysis Exercise 147
(a) Name the electrode formed by the article which is to be plated.
(b) What ions must be present in the electrolyte?
(c) What should be the nature of the anode?
(b) The ions of the metal which is to be electroplated must be present in the electrolyte.
(c) The metal to be plated on the article must be made anode. It needs to be periodically replaced.
(a) What ions must be present in the electrolyte?
(b) Of what substance must the anode be made up of?
(c) What will the cathode be made up of?
(d) Write the equation for the reaction which takes place at the cathode.
(i) Ions only:- HCl
(ii) Molecules only:- Petrol
(iii) Both ions and molecules:- CH3COOH
(b) What are the particles present in a compound which is a non- electrolyte?
(c) If an electrolyte is described as a 'strong electrolyte' what does this mean?
(b) Non- electrolyte are substances which do not conduct electricity in fused or aqueous state. They contain only molecules and do not ionize. For example: petrol, alcohol.
(c) If the electrolyte is described as 'strong electrolyte' it means it completely dissociates into its constituting ions in aqueous solution.
(a) Compare the change in mass of the anode
(b) What is seen to happen to the colour of the copper sulphate solution if platinum electrodes are used? Explain the observation.
(c) What is the practical application of the electrolysis of copper sulphate solution? Briefly, describe one such application.
(b) When platinum rods are used as electrodes, then x the blue colour of copper sulphate solution fades and sulphuric acid is formed. This is because oxygen is liberated at anode and copper metal is deposited at cathode
(c) Practical application of electrolysis of copper sulphate solution: This is the basis for purification of copper.
Other metals like Zinc, Nickel, Silver .Lead can also be purified.
Chapter 6 - Electrolysis Exercise 148
To electroplate an article with nickel requires an (a) ________ which must be a solution containing (b) ________ions. The article to be plated is placed as the (c) _________of the cell in which the plating is carried out. The (d)________ of the cell is made from pure nickel. The ions that are attracted to the negative electrode and discharged are called (e)________.
The electrolysis of lead bromide liberates lead and bromine.
(a) Strong electrolytes (b) weak electrolytes ( c) non- electrolytes
Acetic acid, ammonium chloride, ammonium hydroxide, carbon tetrachloride, dilute hydrochloric acid, sodium acetate, dilute sulphuric acid.
(b) Weak electrolyte - Acetic acid, Ammonium hydroxide
(c) Non-electrolytes - Carbon tetrachloride
(i) Pure water consists entirely of ________ ( ions/ molecules).
(ii) We can expect that pure water _______ ( will / will not) normally conduct electricity.
(ii) will not
(b) Copy and complete the following sentence :
With platinum electrodes, hydrogen is liberated at the ______and oxygen at the _________ during the electrolysis of acidified water.
(b) Cathode, Anode
Electrolysis is the passage of __________ (electricity/electrons) through a liquid or solution accompanied by a __________ ( physical/chemical ) change.
Chapter 6 - Electrolysis Exercise 149
(a) Write equations to show how X and Y form ions.
(b) If Y is diatomic gas, write the equation for the direct combination of X and Y to form a compound.
(c) Write two applications of electrolysis in which anode diminish in mass.
(d) If the compound formed between X and Y is melted and an electric current passed through the molten compound, the element X will be obtained at the _____ and the Y at the ________of the electrolytic cell. (Provide the missing words).
(b) If HX is a weak acid, what particles will be present in its dilute solution apart from those of water?
(c) Cations are formed by _______ (loss/ gain) of electrons and anions are formed by ________( loss/gain) of electrons.
(Choose the correct words to fill in the blanks.)
(d) What ions must be present in a solution used for electroplating a particular metal?
(e) Explain how electrolysis is an example of Redox reaction.
(b) Non ionized molecules; H+ and X- particles will be present in dilute solution.
(c) Loss, Gain
(d) The ions of the metal which is to be electroplated on the article must be present in a solution.
(e) Redox reaction is one in which oxidation and reduction occurs simultaneously.
Similarly in case of electrolysis:
At cathode: The cations gain electron and become neutral. As the electrons are gained the ion is said to be reduced.
At anode: The anions lose electron to form neutral atoms. As the electrons are lost the ion is said to be oxidized.
Hence in electrolysis also the oxidation and reduction occurs hence it is an example of Redox reaction.
(ii) Name the gas released at the cathode when acidulated water is electrolyzed.
(iii) Explain, why solid sodium chloride does not allow electricity to pass through?
(iv) Fill in the blanks:
(a) As we descend the electrochemical series containing cations, the tendency of the cations to get ________ (oxidized/reduced) at the cathode increases.
(b) The (higher/lower) _______ the concentration of an ion in a solution, the greater is the probability of its being discharged at its appropriate electrode.
(ii) Hydrogen is released at the cathode when acidulated water is electrolyzed.
(iii) In sodium chloride, Na+ and Cl- ions are not free to carry the electric current.
(iv) (a) Reduced
(A) Non-electrolyte, (B) Strong electrolyte, (C) Weak electrolyte, (D) Metallic conductor
(i) Molten ionic compound
(ii) Carbon tetrachloride
(iii) An aluminium wire
(iv) A solution containing solvent molecules, solute molecules and ions formed by the dissociation of solute molecules
(v) A sugar solution with sugar molecules and water molecules.
(ii) Carbon tetrachloride- Non-electrolyte
(iii) An aluminium wire- Metallic conductor
(iv) A solution containing solvent molecules, solute molecules and ions formed by the dissociation of solute molecules- weak electrolyte
(v) A sugar solution with sugar molecules and water molecules- Non-electrolyte
Chapter 6 - Electrolysis Exercise 150
(a) Which solution is used to react with bauxite as first step in obtaining pure aluminium oxide?
(b) The aluminium oxide for the electrolytic extraction of aluminium is obtained by heating aluminium hydroxide. Write the equation for this reaction.
(c) Name the element which serves both as the anode and the cathode in the extraction of aluminium.
(d) Write the equation for the reaction that occurs at the cathode during the extraction of aluminium.
(e) Write the equation for the reaction that occurs at the cathode during extraction of aluminium by electrolysis.
(f) Give the equation for the reaction that occurs at the anode when aluminium is purified by electrolysis.
During the electrolysis of molten lead bromide, which of the following takes place?
(a) Bromine is released at the cathode
(b) Lead is deposited at the anode
(c) Bromine ions gain electrons
(d) Lead is deposited at the cathode
(b) At electrode A.
(c) Two compounds in the electrolyte are Al2O3 and Na3AlF6
(d) As at electrode B the oxygen is liberated during the process. The oxygen liberated oxidizes the carbon anode producing CO and CO2.Thus electrode B is to be replaced continuously.
(a) What kind of salt is sodium argento cyanide?
(b) Why is it preferred to silver nitrate as an electrolyte?
(c) State one condition to ensure that the deposit is smooth, firm and long lasting.
(d) Write the reaction taking place at the cathode.
(e) Write the reaction taking place at the anode.
Chapter 6 - Electrolysis Exercise 151
Find the odd one out from the following and explain your choice:
Mg(OH)2 as it is basic while rest are amphoteric.
Lead bromide conducts electricity.
(b) Nickel ions.
Select the correct answer from the choices a,b,c and d which are given. Write only the letter corresponding to the correct answer.
(i) A compound which liberates reddish brown gas around the anode during the electrolysis in its molten state is :
(a) Sodium chloride
(b) Copper (II) oxide
(c) Copper (II) sulphate
(d) Lead (II) bromide
(ii) During ionization metals lose electrons, this change can be called
(i) Lead (II) bromide
Mr Ramu wants electrolyte his key chain with nickel to prevent rusting. For this electroplating
(i) Name the electrolyte
(ii) Name the cathode
(iii) Name the anode
(iv) Give the reaction at the cathode
(v) Give the reaction at the anode
(i) Aqueous solution of nickel sulphate with few drops of dil. sulphuric acid
(ii) Article (e.g. key chain)
(iii) Pure nickel
(iv) Ni2+ + 2e-→ Ni
(v) Ni → Ni2+ + 2e-
Three different electrolytic cells, A,B, and C are conncted in separate circuits. Electrolytic cell A contains sodium chloride solution. When the circuit is completed a bulb in the circuit glows brightly. Electrolytic cell B contains acetic acid solution and in this case the bulb in the circuit glows dimly. The electrolytic cell C contains sugar solution and the bulb does not glow. Give a reason for each of these observations
Cell A contains sodium chloride solution which is a strong
electrolyte and contains only ions. So, it conducts electricity
and the bulb glows brightly.
Cell B contains both ions and molecules. So, there are few
ions to conduct electricity and the bulb glows dimly.
Cell C contains sugar solution which is a non-electrolyte and
does not contain ions. So, it is a bad conductor of electricity
and the bulb does not glow.
Give reasons as to why - the electrolysis of acidulated water is considered to be an example of catalysis.
Dilute sulphuric acid catalyses dissociation, so electrolysis of acidified water is considered an example of catalysis.
Fill in the blanks from the choices given below :
(i) In covalent compounds, the bond is formed due to the ______ (sharing/transfer) of electrons.
(ii) Electro covalent compounds have a _____ (low/high) boiling point
(iii) A molecule of _____ contains a triple bond (hydrogen, ammonia, nitrogen).
(i) In covalent compounds, the bond is formed due to the sharing of electrons.
(ii) Electro covalent compounds have a high boiling point.
(iii) A molecule of nitrogen contains a triple bond.
Differentiate between electrical conductivity of copper sulphate solution and copper metal
Copper sulphate solution
Conduction of electricity is
due to the flow of ions.
Conduction of electricity is
due to the flow of electrons.
It is an aqueous solution of
an ionic compound.
It is a metal in the solid
It undergoes a chemical
It remains unchanged
During the electrolysis of copper (II) sulphate solution using platinum as cathode and carbon an anode:
(i) What do you observe at the cathode and at the anode?
(ii) What change is noticed in the electrolyte?
(iii) Write the reactions at the cathode and at the anode.
(i) Red shiny metal is deposited at the cathode.
(ii) The colour of the electrolytes changes gradually from blue to colourless.
(iii) At the cathode:
Cu2+ + 2e- → Cu
Reaction at the anode:
OH- → OH + e-
4OH → 2H2O + O2
Chapter 6 - Electrolysis Exercise 152
Copper sulphate solution is electrolyzed using copper electrodes
Study the diagram given alongside and answer the questions that follows.
(i) Which electrode to your left or right is known as the oxidizing electrode and why?
(ii) Write the equation representing the reaction that occurs
(iii) State two appropriate observations for the above electrolysis reactions.
(i) The right electrode is the anode and oxidising electrode Cu → Cu2+ + 2e- losing electrode.
(ii) Reaction at the anode: Cu → Cu2+ + 2e-
Reaction at the cathode: Cu2+ + 2e- → Cu
(iii) The anode dissolves and anode mud containing precious metal is recovered.
Which of these will act as a non-electrolyte?
(i) Liquid carbon tetrachloride
(ii) Acetic acid
(iii) Sodium hydroxide aqueous solution acid
(iv) Potassium chloride aqueous solution
(i) Liquid carbon tetrachloride
State one observation when electricity is passed through molten lead bromide.
Dark reddish brown fumes of bromine evolve at the anode and greyish white metal lead is formed on the cathode.
When fused lead bromide is electrolyzed we observe
(i) A silver grey deposit at anode and a reddish brown deposit at cathode
(ii) A silver grey deposit at cathode and reddish brown deposit at anode
(iii) A silver grey deposit at cathode and reddish brown fumes at anode
(iv) Silver grey fumes at anode and reddish brown fumes at cathode
(iii) A silver grey deposit at the cathode and reddish brown fumes at the anode.
The electrolyte used for electroplating an article with silver is:
(i) Silver nitrate solution
(ii) Silver cynide solution
(iii) Sodium argentocyanide solution
(iv) Nickel sulphate solution
(iii) Sodium argentocyanide solution
M is a metal above hydrogen in the activity series and its oxide has the formula M2O. The oxide when dissolved in water forms the corresponding hydroxide which is a good conductor of electricity. In the above context answer the following:
(i) What kind of combination exists between M and O?
(ii) How many electrons and there in the outermost shell of M?
(iii) Name the group to which M belongs
(iv) State the reaction taking place in the cathode
(v) Name the product at the anode
(i) Electrovalent or ionic compounds
(ii) One electron
(iii) Since it has valency 1, M belongs to Group 1.
(iv) At the cathode: M+ + 1e- → M
(v) At the anode: Oxygen gas
Give appropriate scientific reasons for the following statements:
(i) Zinc oxide can be reduced to zinc by using carbon monoxide, but aluminium oxide cannot be reduced by a reducing agent
(ii) Carbon tetrachloride does not conduct electricity.
(iii) During electrolysis of molten lead bromide graphite anode is preferred to other electrodes
(iv) The electrical conductivity of acetic acid is less in comparision to the electrical conductivity of dilute sulphuric acid at a given concentration
(v) Electrolysis of molten lead bromide is considered to be a redox reaction
(i) Zinc is lower in the reactivity series, so it is comparatively less reactive. Hence, it is reduced by using carbon monoxide. But aluminium is very reactive; hence, it cannot be reduced by using a reducing agent and it can be reduced only by electrolytic reduction.
(ii) Carbon tetrachloride is a liquid and does not conduct electricity because it is a covalent compound and there are no free ions present and it contains only molecules.
(iii) In electrolysis of molten lead bromide, reactive bromine is liberated at the anode. As bromine is very reactive, an inert electrode like graphite is preferred in the electrolysis of molten lead bromide.
(iv) Acetic acid is a weak acid and has fewer ions, so conductivity is less, whereas dilute sulphuric acid is a strong acid and has more ions, and therefore, its electrical conductivity is more.
(v) During electrolysis of lead bromide, there is loss of electrons at the anode by bromine and gain of electrons at the cathode by lead. Thus, oxidation and reduction occur side by side. So, it is a redox reaction.
PbBr2 ⇌ Pb+2 + 2Br-
Differentiate between the terms strong electrolyte and weak electrolyte (stating any two differences)
Electrolytes which allow a large amount of electricity to flow through them.
Electrolytes which allow small amounts of electricity to flow through them.
These are good conductors of electricity.
These are poor conductors of electricity.
These almost completely dissociate in the fused or aqueous solution state.
These are partially dissociated in the fused or aqueous solution state.
These solutions contain only free mobile ions.
These solutions contain ions as well as molecules.
Chapter 6 - Electrolysis Exercise 153
(i) Copy and complete the following table :
Purification of copper
(ii) Write the equation taking place at the anode.
Purification of copper
(ii) Ag - e- → Ag+
Cu - e- → Cu2+
Cl⁻ ‒ e- → Cl
Cl + Cl → Cl2
Give reasons why:
(i) Sodium chloride will conduct electricity only in fused or aqueous solution state
(ii) In the electroplating of an article with silver, the electrolyte sodium argento-cynide solution is preferred over silver nitrate solution
(iii) Although copper is a good conductor of electricity, it is a non-electrolyte.
(i) Electrostatic forces of attraction between ions in the solid state are very strong. These forces weaken in the fused state or in the solution state. Hence, ions become mobile.
(ii) If silver nitrate solution is used directly instead of double cyanide of silver and sodium, the deposition of silver will be very fast and hence not very smooth and uniform.
(iii) Copper has no mobile electrons in the solid state and an electrolyte should dissociate into oppositely charged ions to conduct electricity.
Hence, copper is a non-electrolyte.
(i) Name the product formed at the anode during the electrolysis of acidified water using platinum electrodes
(ii) Name the metallic ions that should be present in the electrolyte when an article made copper is to be electroplated with silver
(i) Oxygen is the product formed at the anode.
(ii) Ag+ and Na+
Write equations for the reactions taking place at the two electrodes (mentioning clearly the name of the electrodes) during the electrolysis of
(i) Acidified copper sulphate solution with copper electrodes
(ii) Molten lead bromide with inert electrodes
Reaction at the cathode: Cu2+ + 2e-→ Cu
Reaction at the anode: 4OH- - 4e-→ 4OH
2OH + 2OH →2H2O + O2
(ii) The cathode and anode are both made of graphite plates.
Reaction at the cathode: Pb2+ + 2e-→Pb
Reaction at the anode: Br- - e-→Br
Br + Br →Br2
Identify the substance underlined in each of the following cases:
(a) The electrolyte used for electroplating an article with silver.
(b) The particles present in a liquid such as kerosene, that is non-electrolyte.
(i) The electrolyte used for electroplating an article with silver: Sodium argentocyanide or potassium argentocyanide
(ii) The particles present in a liquid such as kerosene that is a non-electrolyte: Molecules
State the observations at the anode and at the cathode during the electrolysis of :
(a) Fused lead bromide using graphite electrodes
(b) Copper sulphate solution using copper electrodes
Anode: Dark reddish brown fumes of bromine evolve at the anode.
Cathode: Greyish white metal lead is formed on the cathode.
Anode: Nothing gets deposited on the anode because the copper anode dissolves during the reaction as Cu2+ ions are formed.
Cathode: Reddish brown Cu is deposited.
Select the ion in each case, that would get selectively discharge from the aqueous mixture of the ions listed below :
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