Selina Concise Chemistry Solution for ICSE Class 10 Chapter 6 Electrolysis

Electrolysis is actually an interesting chapter that is found in Selina textbook for class 10 chemistry. The chapter deals with understanding what is electrolysis and students will learn how the process actually works based on different situations or perspectives. Students will also study the products of electrolysis and reactions in this chapter. This topic is very important and as many questions can be asked from this unit, we are providing free concise Chemistry class 10 ICSE Solutions for chapter 6 here.

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1. Give reasons for the following:

1. Electrolysis of molten lead bromide is considered to be a reaction in which oxidation and reduction go side by side, i.e., a redox reaction.
2. The blue colour of aqueous copper sulphate fades when it is electrolysed using platinum electrodes.
3. Lead bromide undergoes electrolytic dissociation in the molten state but it is a non-electrolyte in the solid-state.
4. Aluminium is extracted from its oxide by electrolytic reduction and not by conventional reducing agents.
5. The ratio of hydrogen and oxygen formed at the cathode and anode is 2:1 by volume.
6. In the electrolysis of acidified water dilute sulphuric acid is preferred to dilute nitric acid for acidification.
7. Ammonia is unionized in the gaseous state but in the aqueous solution, it is a weak electrolyte.
8. A graphite anode is preferred to other inert electrodes during electrolysis of fused lead bromide.
9. For electroplating with silver, silver nitrate is not used as an electrolyte.
10. Carbon tetrachloride is a liquid but does not conduct electricity.
11. Potassium is not extracted by electrolysis of its aqueous salt solution.

Solution:

1. During lead bromide electrolysis, bromine loses electrons at the anode whereas lead gains electrons at the cathode. Hence, it is a redox reaction because reduction and oxidation occur simultaneously.
2. As the concentration of Cu²⁺ ions decreases the blue colour of the copper ions starts fading. As soon as the concentration of Cu²⁺ ions is finished, the solution becomes colourless.
3. The ions of molten lead bromide are free and loosely packed. In the solid-state, the ions are packed tightly due to the electrostatic force of attraction. Thus, lead bromide undergoes electrolytic dissociation in the molten state.
4. Aluminium cannot be reduced by the reducing agent because of its greater affinity towards oxygen. That is why it is extracted from its oxide by electrolytic reduction.
5. In the electrolytic reactions, 4H¹⁺ is required at the cathode while 4OH^– at the anode while two molecules of oxygen are produced at the anode. Two hydrogen molecules and one oxygen molecule are liberated at the cathode and anode respectively for every two molecules of water. Hence, the ratio of hydrogen and oxygen is 2:1 at cathode and anode.
6. Dilute nitric acid is volatile in nature. Hence, dilute sulphuric acid is preferred to dilute nitric acid.
7. Ammonia, being a covalent compound, is unionized in the gaseous state but forms NH₄OH in aqueous solution which can dissociate into ions.
8. Graphite is unaffected by the bromine vapours evolved during electrolysis of lead bromide. Hence it is preferred over any other electrode.
9. If silver nitrate is used in the electroplating of silver, the silver deposition will be very quick and will not be uniform and smooth.
10. Carbon tetrachloride is a covalent compound and has no free ions. It only contains molecules. Therefore, it does not contain electricity.
11. Potassium reacts with water. Hence it cannot be by the electrolysis of its aqueous salt solution.

2. Copy and complete the following table which shows two practical applications of electrolysis.

Solution:

3. Element X is a metal with valency 2. Element Y is a non-metal with valency 3.

1. Write equations to show how X and Y form ions.
2. If Y is a diatomic gas, write an equation for the direct combination of X and Y to form a compound.
3. If the compound formed between X and Y is melted and an electric current is passed through the molten compound, element X will be obtained at the ________ and Y at the ________ of the electrolytic cell.

Solution:

1. X → X²⁺ + 2e^– ; Y + 3e^– → Y^3-
2. Y₂ + 3X → X₃ Y₂
3. Cathode, anode

3. Write two applications of electrolysis in which anode diminishes in mass.

Solution:

The two applications include electroplating and electrorefining of metals.

4. A strip of copper is placed in four different colourless salt solutions. They are KNO₃, AgNO₃, Zn(NO₃)₂, Ca(NO₃)₂. Which of the solutions will finally turn blue?

Solution:

AgNO₃ turns blue. This is because copper being higher in the electrochemical series displaces silver and forms Cu(NO₃)₂ which is blue in colour.

5. Select the right answer. The aqueous solution of the compound which contains both ions and molecules is:

1. H₂SO₄
2. HCl
3. HNO₃
4. CH₃COOH

Solution:

CH₃COOH contains both ions and molecules.

6. Correct the given statement: “Lead bromide conducts electricity.”

Solution:

Molten lead bromide conducts electricity.

7. The aqueous solution of Nickle sulphate contains Ni²⁺ and SO₄ ^2- ions.

1. Which ion moves towards cathode?
2. What is the product at the anode?

Solution:

1. Ni²⁺ ions move towards the cathode.
2. Oxygen gas is produced at the anode.

8. During electroplating of an article with nickel,

(i) Name

1. The electrolyte
2. The cathode
3. The anode

(ii) Give the reaction of electrolysis at

1. The cathode
2. The anode

Solution:

(i) a. Nickel sulphate

     b. Article

c. Pure nickel plate

(ii) a. Ni²⁺ + 2e^– → Ni

b. Ni – 2e^– →  Ni²⁺

9. Give reason: Electrolysis of acidulated water is considered to be an example of electrolysis.

Solution:

Dilute sulphuric acid acts as a catalyst in dissociation, therefore, it is an example of catalysis.

10. Differentiate between the electrical conductivity of copper sulphate solution and that of copper metal.

Solution:

11. Match the columns:

Solutions:

Ammonium hydroxide solution – Contains ions and molecules

Dilute hydrochloric acid – Contains only ions

Carbon tetrachloride – Contains only molecules

12. Give reason: An aqueous solution of sodium chloride conducts electricity.

Solution:

There are free sodium and chloride ions in the aqueous solution of sodium chloride. This allows a large amount of electricity to pass through it.

13. State which of these will act as a non-electrolyte:

1. Liquid carbon tetrachloride
2. Acetic acid
3. Sodium hydroxide aqueous solution
4. Potassium chloride aqueous solution

Solution:

Liquid carbon tetrachloride acts as a non-electrolyte.

14. Identify a gas which cannot conduct electricity in the liquid state but conducts electricity when dissolved in water.

Solution:

The gas is Hydrogen chloride.

15. Give one word for Electrolytic deposition of a superior metal on a baser metal.

Solution:

Galvanisation

16. State which electrode: anode or cathode is an oxidising electrode? Give a reason for the same.

Solution: 

The anode is the oxidising electrode. Here, the electrons are lost by the anions to form neutral atoms. Due to the loss of electrons, the ions are said to be oxidised.

17. Give reasons why:

1. Sodium chloride conducts electricity only infused or aqueous solution state.
2. In the electroplating of an article with silver, the electrolyte sodium argentocyanide solution is preferred over silver nitrate solution.
3. Although copper is a good conductor of electricity, it is a non-electrolyte.

Solution:

1. In the solid-state, the electrostatic forces of attraction between molecules are very strong. These forces weaken in the fused state and the ions become mobile.
2. Silver deposits very fast and is not smooth and uniform. Hence silver nitrate solution is not used in the electroplating of an article with silver.
3. Copper contains free electrons. The movement of free electrons conducts electricity. But copper does not dissociate into ions. Hence, it is a non-electrolyte.

18. M₂O is the oxide of metal “M” which is above hydrogen in the activity series. M₂O, when dissolved in water, forms the corresponding hydroxide which is a good conductor of electricity. 

1. Stae the reaction taking place at the cathode.
2. Name the product at the anode.

Solution:

1. M⁺ + 1e^– → M
2. Oxygen gas is produced at the anode.

19. Name the kind of particles present in

1. Sodium hydroxide solution
2. Carbonic acid
3. Sugar solution

Solution:

1. Na⁺ ions and OH^– ions
2. H⁺, HCO₃, CO₃^2- ions and H₂CO₃ molecules
3. C₁₂H₂₂O₁₁ molecules

20. State an observation for Electricity is passed through molten bromide.

Solution:

Greyish white metal lead is formed at the cathode while dark reddish-brown fumes are formed at the anode.

These solutions will significantly help students be confident and tackle even the difficult questions from this chapter. Besides, these solutions contain detailed explanations and well-written answers that will not only help students understand the concepts clearly but they will also get an insight into the important questions and topics to study. Students can use these solutions to study productively and perform well in the exams.

The given solutions are as per the 2019-20 Concise Selina textbook. The Selina Solutions for the academic year 2020-21 will be updated soon.