NCERT Solutions for Class 12 Chemistry Chemistry Part-1 Chapter 3

Electrochemistry Class 12

Chapter 3 Electrochemistry Exercise Solutions

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In text : Solutions of Questions on Page Number : 68

Q1 :  

How would you determine the standard electrode potential of the systemMg2+| Mg?


Answer :

The standard electrode potential of Mg2+| Mg can be measured with respect to the standard hydrogen electrode, represented by Pt(s), H2(g)(1 atm) | H+(aq)(1 M).

A cell, consisting of Mg | MgSO4(aq 1 M) as the anode and the standard hydrogen electrode as the cathode, is set up.

Then, the emf of the cell is measured and this measured emf is the standard electrode potential of the magnesium electrode.

Here, for the standard hydrogen electrode is zero.

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Q2 :  

Can you store copper sulphate solutions in a zinc pot?


Answer :

Zinc is more reactive than copper. Therefore, zinc can displace copper from its salt solution. If copper sulphate solution is stored in a zinc pot, then zinc will displace copper from the copper sulphate solution.

Hence, copper sulphate solution cannot be stored in a zinc pot.

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Q3 :  

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


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Q4 :  

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


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Q5 :  

Calculate the emf of the cell in which the following reaction takes place:

Given that = 1.05 V


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Q6 :  

The cell in which the following reactions occurs:

has = 0.236 V at 298 K.

Calculate the standard Gibbs energy and the equilibrium constant of the cell reaction.


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Q7 :  

Why does the conductivity of a solution decrease with dilution?


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Q8 :  

Suggest a way to determine the value of water.


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Q9 :  

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 and λ °(HCOO-) = 54.6 S cm2 mol


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Q10 :  

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


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Q11 :  

Suggest a list of metals that are extracted electrolytically.


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Q12 :  

What is the quantity of electricity in coulombs needed to reduce 1 mol of

? Consider the reaction:


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Q13 :  

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


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Q14 :  

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


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Q15 :  

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


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<< Previous Chapter 2 : Solutions Next Chapter 4 : Chemical Kinetics >>

Exercise : Solutions of Questions on Page Number : 92

Q1 :  

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


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Q2 :  

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.


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Q3 :  

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.


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Q4 :  

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.


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Q5 :  

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).


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Q6 :  

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 and for the reaction.


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Q7 :  

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


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Q8 :  

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


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Q9 :  

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 x 10-3 S cm-1.


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Q10 :  

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

Concentration/M 0.001 0.010 0.020 0.050 0.100

102 × ÃŽÂº/S m - 1 1.237 11.85 23.15 55.53 106.74

Calculate for all concentrations and draw a plot between and c ½. Find the value of.


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Q11 :  

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


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Q12 :  

How much charge is required for the following reductions:

(i) 1 mol of Al3+ to Al.

(ii) 1 mol of Cu2+ to Cu.

(iii) 1 mol of to Mn2+.


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Q13 :  

How much electricity in terms of Faraday is required to produce

(i) 20.0 g of Ca from molten CaCl2.

(ii) 40.0 g of Al from molten Al2O3.


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Q14 :  

How much electricity is required in coulomb for the oxidation of

(i) 1 mol of H2O to O2.

(ii) 1 mol of FeO to Fe2O3.


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Q15 :  

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?


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Q16 :  

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?


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Q17 :  

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

(i) Fe3+(aq) and I-(aq)

(ii) Ag+ (aq) and Cu(s)

(iii) Fe3+ (aq) and Br- (aq)

(iv) Ag(s) and Fe3+ (aq)

(v) Br2 (aq) and Fe2+ (aq).


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Q18 :  

Predict the products of electrolysis in each of the following:

(i) An aqueous solution of AgNO3 with silver electrodes.

(ii) An aqueous solution of AgNO3with platinum electrodes.

(iii) A dilute solution of H2SO4with platinum electrodes.

(iv) An aqueous solution of CuCl2 with platinum electrodes.


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Chemistry Part-1 - Chemistry : CBSE NCERT Exercise Solutions for Class 12th for Electrochemistry will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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