S.P. Singh solutions for Concise Chemistry [English] Class 10 ICSE chapter 6 - Electrolysis [Latest edition]

Powdered sodium chloride (common salt) does not conduct an electric current, but it does so when ______ or when ______.

Molten lead bromide conducts electricity. It is called an ______. It is composed of lead ______ and bromide ______. The lead ions are ______ charged and are called ______. The bromide ______ are ______ charged and are called ______.

Substances which conduct electricity in the solid state are generally ______.

The electron releasing tendency of zinc is ______ than that of copper. 

A solution of HCl gas in water conducts electricity because ______, but a solution of HCl gas in toluene does not conduct an electric current because ______.

Pure water consists entirely of ______.

We can expect that pure water ______ normally conducts electricity.

Electrolysis is the passage of ______ through a liquid or a solution accompanied by a ______ change.

When the current is turned on, electrons flow from ______ (anode/cathode) to ______ (anode/cathode). The cathode becomes the ______ (negative/positive) electrode by which electrons ______ (enter/leave) the electrolyte.

Define the following term: 

Electrolysis

Define the following term: 

Non-electrolyte 

Define the following term:

Cation

Define the following term:

anion

Define the following term:

Weak electrolytes

What is the difference between:

Modern explanation and Arrhenius explanation for the theory of electrolysis.

What is the difference between:

Electrolytic dissociation and ionisation.

What is the difference between:

A cation and an anion.

What is the difference between:

Electrolytic dissociation and thermal dissociation.

What is the difference between:

Strong electrolyte and weak electrolyte.

Name a salt which is a weak electrolyte.

Name a base which is a weak electrolyte.

Name an inert electrode.

Name an active electrode.

Name a positively charged non-metallic ion.

Name the electrode at which reduction occurs.

Name a non-metallic element which is a conductor of electricity.

Electrolysis is a redox process. Explain.

Classify the following substances under three headings:

1. strong electrolytes
2. weak electrolytes
3. non-electrolytes

Acetic acid, ammonium chloride, ammonium hydroxide, carbon tetrachloride, dilute hydrochloric acid, sodium acetate, dilute sulphuric acid.

Explain why Cu, though a good conductor of electricity is a non electrolyte?

Explain why solid sodium chloride does not allow electricity to pass through?

Complete and state whether the reaction is oxidation or reduction.

\[\ce{Cl- - e- ->}\] .........

Complete and state whether the reaction is oxidation or reduction.

\[\ce{Al -}\] .......... \[\ce{-> Al^{3+}}\]

Complete and state whether the reaction is oxidation or reduction.

\[\ce{Pb^{2+} +}\] .......... \[\ce{-> Pb}\]

Complete and state whether the reaction is oxidation or reduction.

\[\ce{Sn^{4+} +}\] .......... \[\ce{-> Sn^{2+}}\]

Name two substances in the following case:

Contain only molecules.

Name two substances in the following case:

Contain only ions.

Name two substances in the following case:

Contain ions as well as molecules.

Select the ion in the following case, that would get selectively discharged from the aqueous mixture of the ions listed below:

\[\ce{SO^2-_4, NO^-_3 {and} OH-}\]

Select the ion in the following case, that would get selectively discharged from the aqueous mixture of the ions listed below:

Pb²⁺, Ag⁺ and Cu²⁺

Among Zn and Cu, which would occur more readily in nature as metal and which as an ion?

Why cannot we store AgNO₃ solution in copper vessel?

Out of Cu and Ag, which is more active?

How would you change a metal like Cu into its ions?

How would you change Cu²⁺ ion to Cu?

A solution of caustic soda (NaOH) in water or when fused, conducts an electric current. what is the similarity in these two cases?

During electrolysis of an aqueous solution of sulphuric acid between platinum electrodes, two types of anions migrate towards the anode but only one of them is discharged:

1. Name the two anions.
2. Name the main product of the discharge of anion at the anode and write the anode reaction.
3. Name the product at the cathode and write the reaction.
4. Do you notice any change in colour. State why?
5. Why this electrolysis, is considered as an example of catalysis?

Copper sulphate solution is electrolysed using a platinum cathode and carbon anode.

Study the diagram given alongside and answer the following questions:

1. Give the names of the electrodes A and B.
2. Which electrode is the oxidising electrode?

Explain the following:

A solution of cane sugar does not conduct electricity, but a solution of sodium chloride is a good conductor.

Explain the following:

Hydrochloric acid is a good conductor of electricity.

Explain the following:

During the electrolysis of an aqueous solution of NaCI, hydrogen ion is reduced at the cathode and not the sodium ion though both Na⁺ and H⁺ ions are present in the solution.

Explain the following:

On electrolysis of dilute copper (II) sulphate solution, copper is deposited at the cathode but no hydrogen gas evolves there. Explain why?

Explain the following: 

When a dilute aqueous solution of sodium chloride is electrolysed between platinum electrodes, hydrogen gas is evolved at the cathode but metallic sodium is not deposited. Why?

Explain the following: 

Zinc can produce hydrogen on reacting with acids but copper cannot. 

To carry out the so-called "electrolysis of water", sulphuric acid is added to water. How does the addition of sulphuric acid produce a conducting solution?

AB₂ is a hard crystalline solid having high melting and boiling points. It conducts electricity in aqueous and molten states.

1. AB₂ conducts electricity due to the presence of free ______ (ions/molecules/electrons).
2. During electrolysis of AB₂ in aqueous state, it is observed that cathode becomes thick and anode thin. The anode material will be ______ (graphite/metal A).

Give reason for the following:

The blue colour of aqueous copper sulphate fades when it is electrolysed using platinum electrodes.

Give reason for the following:

Lead bromide undergoes electrolytic dissociation in the molten state but is a non-electrolyte in the solid state.

Give reason for the following:

Aluminium is extracted from its oxide by electrolytic reduction and not by convectional reducing agents.

Give reason for the following:

The ratio of hydrogen and oxygen formed at the cathode and anode is 2 : 1 by volume.

Give reason for the following:

In the electrolysis of acidified water, dilute sulphuric acid is preferred to dilute nitric acid for acidification.

Give reason for the following:

Ammonia is unionised in the gaseous state but in the aqueous solution, it is a weak electrolyte.

Give reasons for the following:

A direct current instead of alternating current should be used in electrolysis.

During the electrolysis of molten lead bromide, which of the following takes place?

The aqueous solution of the compound which contains both ions and molecules is ______.

A compound which during electrolysis in its molten state, liberates a reddish brown gas at the anode.

Identify the weak electrolyte from the following:

An aqueous electrolyte consists of the ions mentioned in the list. The ion which could be discharged most readily during electrolysis.

An electrolyte which completely dissociates into ions is ______.

During silver plating of an article using potassium argentocyanide as an electrolyte, the anode material should be.

Which of these will act as a non-electrolyte?

The observation seen when fused lead bromide is electrolysed is ______.

During electroplating an article with silver, the electrolyte used is ______.

The metallic electrode which does not take part in an electrolytic reaction.

The ion which is discharged at the anode during the electrolysis of copper sulphate solution using platinum electrodes as anode and cathode.

When dilute sodium chloride is electrolysed using graphite electrodes, the cation which is discharged at the cathode most readily.

Cathode is a reducing electrode because ______.

Which statement about conduction of electricity is correct?

The oxidation reaction among the following is:

During electrolysis, what happens to metallic ions and at which electrode do they get discharged?

P Reduction of metallic ions, cathode

Q Oxidation of metallic ions, anode

R Oxidation of metallic ions, cathode

Assertion (A): Electrolysis establishes a relationship between electrical energy and chemical energy.

Reason (R): Substances like metals, carbon (graphite) are conductors while salts like NaCl, KCl are electrolytes.

Assertion (A): Benzene acts as non-electrolyte.

Reason (R): Benzene does not have free ions.

Assertion (A): Metals and alloys conduct electricity with the help of electrons.

Reason (R): Non-metals do not have free electrons.

Assertion (A): Weak electrolytes do not allow any electricity to flow through them.

Reason (R): Substances which are composed of only molecules do not allow any current to flow through them.

Assertion (A): NaCl is an example of an electrolyte.

Reason (R): NaCl conducts electricity in aqueous or molten state.

Assertion (A): An electrolyte can be acid, base or salt.

Reason (R): An electrolyte is a substance which can conduct electricity in aqueous or molten state.

Assertion (A): Oxidation occurs at the anode.

Reason (R): Electrons are gained at the anode.

Assertion (A): Polar covalent compounds can form ions when dissolved in water.

Reason (R): Electrovalent compounds show dissociation.

Assertion (A): A block of pure silver metal is used as anode during silver plating.

Reason (R): Silver ions are deposited as metal at the anode.

Cations are formed by ______ of electrons and anions are formed by ______ of electrons.

Match the following in column A with the correct answer from the choices given in column B:

Choose A, B, C or D to match the descriptions (i) to (v) below . Some alphabets may be repeated.
(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.

Name the kind of particles present in sodium hydroxide solution.

Name the kind of particles present in carbonic acid.

Name the kind of particles present in the sugar solution.

What kind of particles will be found in a liquid compound which is a non-electrolyte?

If HX is a weak acid, what particles will be present in its dilute solution apart from those of water?

What ions must be present in a solution used for electroplating a particular metal?

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

Here is an electrode reaction:

\[\ce{Cu -> Cu^{2+} + 2e^-}\]

At which electrode (anode or cathode) would such a reaction take place? Is this an example of oxidation?

Give one word or phrase for the following:

Electrolytic deposition of a superior metal on a baser metal.

Identify:

A gas which does not conduct electricity in the liquid state but conducts electricity when dissolved in water.

Aqueous solution of nickel sulphate contains \[\ce{Ni^{+2}}\] and \[\ce{SO^{-2}_{4}}\] ions.

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

Give reason for the following:

Carbon tetrachloride is a liquid but does not conduct electricity.

Give reason for the following:

Potassium is not extracted by electrolysis of its aqueous salt solution.

Give reasons as to why - the electrolysis of acidulated water is considered to be an example of catalysis.

Give appropriate scientific reasons for the following statement:

During electrolysis of molten lead bromide, graphite anode is preferred to other electrodes.

Give reason for the following:

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.

Give reasons why sodium chloride will conduct electricity only in the fused or aqueous solution state.

Give reasons why in the electroplating of an article with silver, the electrolyte sodium argentocynide solution is preferred over silver nitrate solution.

Give reasons why although copper is a good conductor of electricity, it is a non-electrolyte.

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

A solution contains magnesium ions (Mg⁺²), iron (II) ions (Fe⁺²) and copper ions (Cu⁺²). On passing an electric current through this solution, which ions will be the first to be discharged at the cathode? Write the equation for the cathode reaction.

During electroplating of an article with nickel, name the electrolyte.

During electroplating of an article with nickel, name the cathode.

During electroplating of an article with nickel, name the anode.

During electroplating of an article with nickel, give the reaction of the electrolysis at the cathode.

During electroplating of an article with nickel, give the reaction of the electrolysis at the anode.

Three different electrolytic cells, A, B and C are connected in separate circuits. Electrolytic cell A contains a sodium chloride solution. When the circuit is completed, a bulb in the circuit glows brightly. Electrolytic cell B contains an acetic acid solution and in this case, the bulb in the circuit glows dimly. The electrolytic cell C contains a sugar solution and the bulb does not glow. Give a reason for each of these observations.

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

State one observation when electricity is passed through molten lead bromide.

State your observation at the cathode, when acidified aqueous copper sulphate solution is electrolysed with copper electrodes.

State one relevant observation for the following:

At the anode when aqueous copper sulphate solution is electrolysed using copper electrodes.

Which electrode—anode or cathode—is the oxidising electrode? Why?

M₂O is the oxide of a 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. State the reaction taking place at the cathode
2. Name the product at the anode.

Choosing only words from the following list, write down the appropriate words to fill in the blanks (a) to (e) below:

anions, anode, cathode, cations, electrode, electrolyte, nickel, voltameter.

The electroplating of 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) ______.

When a molten ionic compound is electrolysed, the metal is always formed at ______ and the non-metal is formed at ______.

Electrolysis of acidulated water is an example of ______.

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

Write equations to show how X and Y form ions?

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

If Y is a diatomic gas, write the equation for the direct combination of X and Y to form a compound.

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

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 Y at the ______ of the electrolytic cell. (Provide the missing words).

Draw a labelled diagram to show how iron is electroplated with copper.

Which solution is preferred as electrolyte, CuSO₄ or FeSO₄?

Describe what happens to the iron object and the copper rod.

A metal article is to be electroplated with silver. The electrolyte selected is sodium argentocyanide.

1. What kind of salt is sodium argentocyanide?
2. Why is it preferred to silver nitrate as an electrolyte?
3. State one condition to ensure that the deposit is smooth, firm and long lasting.
4. Write the reaction taking place at the cathode.
5. Write the reaction taking place at the anode.
   

During the electrolysis of copper (II) sulphate solution using platinum as cathode and carbon as anode:

1. What do you observe at the cathode and at the anode?
2. What change is noticed in the electrolyte?
3. Write the reactions at the cathode and at the anode.

(a) Copy and complete the following table, which refers to two practical applications of electrolysis.

(b) Write the equation taking place at the anode for Q. (a).

The following sketch represents the electroplating of an Iron cup with Nickel metal.

Study the diagram and answer the following questions:

1. During electroplating, the iron cup is placed at the cathode. Why?
2. Name the ion that must be present in the electrolyte.
3. State one condition that is necessary to ensure that the deposit is smooth, firm and even.
4. Write the reaction taking place at the cathode.
5. What change would you observe at the anode?

Copper sulphate solution is electrolyzed using copper electrodes. Study the diagram given alongside and answer the questions that follow.

1. Which electrode to your left or right is known as the oxidizing electrode and why?
2. Write the equation representing the reaction that occurs.
3. State two appropriate observations for the above electrolysis reactions.

Electroplating steel objects with silver involves a three-step process.

Step 1: A coating of copper is applied to the object.

Step 2: A coating of nickel is applied to the object.

Step 3: The coating of silver is applied to the object.

(a) A diagram of the apparatus used for step 1 is shown.

1. The chemical process taking place on the surface of the object is \[\ce{Cu^2+_{ (aq)} + 2e- ->Cu_{(s)}}\].
   What is the observation seen on the surface of the object?
2. Explain why the concentration of copper ions in the electrolyte remains constant throughout step 1. 

(b) Give two changes which would be needed in order to coat nickel onto the object in step 2.

(c) Write down the reaction taking place at the positive electrode during step 3.