# NCERT solutions for Class 12 Chemistry Textbook chapter 3 - Electrochemistry [Latest edition]

## Chapter 3: Electrochemistry

[Pages 68 - 90]

### NCERT solutions for Class 12 Chemistry Textbook Chapter 3 Electrochemistry[Pages 68 - 90]

Q 1 | Page 68

How would you determine the standard electrode potential of the system Mg2+ | Mg?

Q 2 | Page 68

Can you store copper sulphate solutions in a zinc pot?

Q 3 | Page 68

Consult the table of standard electrode potentials and suggest three substances that can oxidise ferrous ions under suitable conditions

Q 4 | Page 73

Calculate the potential of hydrogen electrode in contact with a solution whose pH is 10.

Q 5 | Page 73

Calculate the emf of the cell in which the following reaction takes place:  Ni(s)+2Ag+ (0.002 M) -> Ni2+ (0.160 M)+2Ag(s) Given that E(-)(cell) = 1.05 V

Q 6 | Page 73

The cell in which the following reactions occurs: 2Fe3+ (aq) + 2I– (aq) —> 2Fe2+ (aq) +I2 (s) has E°cell=0.236 V at 298 K. Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.

Q 9 | Page 83

The molar conductivity of 0.025 mol L-1 methanoic acid is 46.1 S cm2 mol-1. Calculate its degree of dissociation and dissociation constant Given λ°(H+)=349.6 S cm2 mol-1 andλ°(HCOO-) = 54.6 S cm2 mol-1

Q 10 | Page 86

If a current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons would flow through the wire?

Q 11 | Page 86

Suggest a list of metals that are extracted electrolytically.

Q 12 | Page 86

Consider the reaction: Cr2O72--+ 14H+ + 6e- -> 2Cr3+ + 7H2O What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2O72- ?

Q 13 | Page 90

Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging.

Q 14 | Page 90

Suggest two materials other than hydrogen that can be used as fuels in fuel cells.

Q 15 | Page 90

Explain how rusting of iron is envisaged as setting up of an electrochemical cell.

[Pages 91 - 92]

### NCERT solutions for Class 12 Chemistry Textbook Chapter 3 Electrochemistry[Pages 91 - 92]

Q 1 | Page 91

Arrange the following metals in the order in which they displace each other from the solution of their salts.

Al, Cu, Fe, Mg and Zn

Q 2 | Page 91

Given the standard electrode potentials,

K+/K = −2.93V, Ag+/Ag = 0.80V,

Hg2+/Hg = 0.79V

Mg2+/Mg = −2.37 V, Cr3+/Cr = − 0.74V

Arrange these metals in their increasing order of reducing power.

Q 3 | Page 91

Depict the galvanic cell in which the reaction Zn(s) + 2Ag+(aq) → Zn2+(aq) + 2Ag(s) takes place. Further show:

(i) Which of the electrode is negatively charged?

(ii) The carriers of the current in the cell.

(iii) Individual reaction at each electrode.

Q 4 | Page 91

Calculate the standard cell potentials of galvanic cells in which the following reactions take place:

(i) 2Cr(s) + 3Cd2+(aq) → 2Cr3+(aq) + 3Cd

(ii) Fe2+(aq) + Ag+(aq) → Fe3+(aq) + Ag(s)

Calculate the ΔrGθ and equilibrium constant of the reactions.

Q 5 | Page 91

Write the Nernst equation and emf of the following cells at 298 K:

(i) Mg(s) | Mg2+(0.001M) || Cu2+(0.0001 M) | Cu(s)

(ii) Fe(s) | Fe2+(0.001M) || H+(1M)|H2(g)(1bar) | Pt(s)

(iii) Sn(s) | Sn2+(0.050 M) || H+(0.020 M) | H2(g) (1 bar) | Pt(s)

(iv) Pt(s) | Br2(l) | Br(0.010 M) || H+(0.030 M) | H2(g) (1 bar) | Pt(s).

Q 6 | Page 91

In the button cells widely used in watches and other devices the following reaction takes place:

Zn(s) + Ag2O(s) + H2O(l) → Zn2+(aq) + 2Ag(s) + 2OH(aq)

Determine triangle_rG^Theta and E^Theta for the reaction.

Q 7 | Page 91

Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration.

Q 8 | Page 91

The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 Scm−1. Calculate its molar conductivity.

Q 8.41 | Page 92

Predict the products of electrolysis in each of the following:

An aqueous solution of CuCl2 with platinum electrodes.

Q 9 | Page 91

The resistance of a conductivity cell containing 0.001M KCl solution at 298 K is 1500 Ω. What is the cell constant if conductivity of 0.001M KCl solution at 298 K is 0.146 × 10−3 S cm−1.

Q 10 | Page 92

The conductivity of sodium chloride at 298 K has been determined at different concentrations and the results are given below:

 Concentration/M 0.001 0.01 0.02 0.05 0.1 102 × κ/S m–1 1.237 11.85 23.15 55.53 106.74

Calculate Lambda_m for all concentrations and draw a plot between Lambda_m and c^(1/2) Find the value of Lambda_m^0

Q 11 | Page 92

Conductivity of 0.00241 M acetic acid is 7.896 × 10−5 S cm−1. Calculate its molar conductivity and if Lambda_m^0 for acetic acid is 390.5 S cm2 mol−1, what is its dissociation constant?

Q 12.1 | Page 92

How much charge is required for the following reductions: 1 mol of Al3+ to Al.

Q 12.2 | Page 92

How much charge is required for the following reductions: 1 mol of Cu2+ to Cu.

Q 12.3 | Page 92

How much charge is required for the following reductions: 1 mol of MnO_4^(-) to Mn2+.

Q 14.1 | Page 92

How much electricity is required in coulomb for the oxidation of 1 mol of H2O to O2.

Q 14.2 | Page 92

How much electricity is required in coulomb for the oxidation of 1 mol of FeO to Fe2O3.

Q 15 | Page 92

A solution of Ni(NO3)2 is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

Q 16 | Page 92

Three electrolytic cells A,B,C containing solutions of ZnSO4, AgNO3 and CuSO4, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?

Q 17.1 | Page 92

Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:

Fe3+(aq) and I(aq)

Q 17.2 | Page 92

Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:

Ag+ (aq) and Cu(s)

Q 17.3 | Page 92

Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:

Fe3+ (aq) and Br− (aq)

Q 17.4 | Page 92

Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:

Ag(s) and Fe3+ (aq)

Q 17.5 | Page 92

Using the standard electrode potentials given in Table 3.1, predict if the reaction between the following is feasible:

Br(aq) and Fe2+ (aq).

Q 18.1 | Page 92

Predict the products of electrolysis in each of the following:

An aqueous solution of AgNO3 with silver electrodes.

Q 18.2 | Page 92

Predict the products of electrolysis of the following:

An aqueous solution of AgNO3with platinum electrodes.

Q 18.3 | Page 92

Predict the products of electrolysis in each of the following:

A dilute solution of H2SO4with platinum electrodes.

## NCERT solutions for Class 12 Chemistry Textbook chapter 3 - Electrochemistry

NCERT solutions for Class 12 Chemistry Textbook chapter 3 (Electrochemistry) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Class 12 Chemistry Textbook solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Class 12 Chemistry Textbook chapter 3 Electrochemistry are Electrochemical Cells, Conductance of Electrolytic Solutions - Introduction, Variation of Conductivity and Molar Conductivity with Concentration, Electrolytic Cells and Electrolysis - Introduction, Primary Batteries, Lead Accumulator, Galvanic Cells - Introduction, Nernst Equation - Introduction, Relation Between Gibbs Energy Change and Emf of a Cell, Galvanic Cells - Measurement of Electrode Potential, Equilibrium Constant from Nernst Equation, Electrochemical Cell and Gibbs Energy of the Reaction, Measurement of the Conductivity of Ionic Solutions, Products of Electrolysis, Secondary Batteries, Fuel Cells, Concept of Corrosion, Introduction to Electrochemistry, Faraday’s Law of Induction.

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