Chemistry

Electrochemistry

Question:

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

Answer:

ncert-solutions-for-class-12-chemistry-electrochemistry-11

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Electrochemistry

Q 1.

Write the cell reaction of a lead storage battery when it is discharged. How does the density of the electrolyte change when the battery is discharged?

Q 2.

Consider a cell given below:
Cu |Cu2+ || Cl |Cl2, Pt
Write the reactions that occur at anode and cathode.

Q 3.

Aqueous copper sulphate solution and aqueous silver nitrate solution are electrolysed by 1 ampere current for 10 minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be same or different? Explain your answer.

Q 4.

Match the items of Column I and Column II.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-51

Q 5.

What advantage do the fuel cells have over primary and secondary batteries?

Q 6.

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 7.

An electrochemical cell can behave like an electrolytic cell when
ncert-exemplar-problems-class-12-chemistry-electrochemistry-7

Q 8.

Use the data given in Q.8 and find out the most stable oxidized species.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-14

Q 10.

What will happen during the electrolysis of aqueous solution of CuSO4  by using platinum electrodes?
(a) Copper will deposit at cathode.
(b) Copper will deposit at anode.
(c) Oxygen will be released at anode.
(d) Copper will dissolve at anode.

Q 11.

Under what condition is
ncert-exemplar-problems-class-12-chemistry-electrochemistry-36

Q 12.

Unlike dry cell, the mercury cell has a constant cell potential throughout its useful life. Why?

Q 13.

Why on dilution the Am of CH3COOH increases drastically, while that of CH4COONa increases gradually?

Q 14.

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 15.

E °ell for some half-cell reactions are given below. On the basis of these marks the correct answer will be
ncert-exemplar-problems-class-12-chemistry-electrochemistry-23
(a) In dilute sulphuric acid solution, hydrogen will be reduced at cathode.
(b) In concentrated sulphuric acid solution, water will be oxidized at anode.
(c) In dilute sulphuric acid solution, water will be oxidized at anode.
(d) In dilute sulphuric acid solution, SO2-ion will be oxidized to tetrathionate ion at anode.

Q 16.

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

Q 17.

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

Q 18.

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

Q 19.

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 Al203?

Q 20.

For the given cell, Mg|Mg2+||Cu2+  || Cu
(a) Mg is cathode
(b) Cu is cathode
(c) The cell reaction Mg + Cu2++ — »Mg2+ + Cu
(d) Cu is the oxidizing agent

Q 21.

What is electrode potential?

Q 22.

Assertion (A): Ecell should have a positive value for the cell to function. Reason (R). Ecadlode Eanode

Q 23.

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 24.

Suggest a list of metals that are extracted electrolytically.

Q 25.

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

Q 26.

Conductivity of 0.00241 M acetic acid is 7.896 x 10-5 S cm-1. Calculate its molar conductivity.  If Λm0, for acetic acid is 390.5 S cm2 mol-1, what is its dissociation constant?

Q 27.

Value of standard electrode potential for the oxidation of Cl ions is more positive than that of water, even then in the electrolysis of aqueous sodium chloride, why is Cl- oxidized at anode instead of water?

Q 28.

The resistance of a conductivity cell containing 0.001 M KCI solution at 298 K is 1500 Ω What is the cell constant if conductivity of 0.001 M KCI solution at 298 K is 0.146 x 10-3 S cm-1?

Q 29.

When acidulated water (dil. H2SO4 solution) is electrolysed, will the pH of the solution be affected? Justify your answer.

Q 30.

Assertion (A): Mercury cell does not give steady potential.
Reason (R): In the cell reaction, ions are not involved in solution.

Q 31.

Suggest a way to determine the value of water.

Q 32.

Predict the products of electrolysis in each of the following.
(i) An aqueous solution of AgNO3 with silver electrodes.
(ii) An aqueous solution of AgNO3 with platinum electrodes.
(iii) A dilute solution of H2S04 with platinum electrodes.
(iv) An aqueous solution of CuCl2 with platinum electrodes.

Q 33.

Using given below find strongest reduction agent.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-8

Q 34.

Molar conductivity of ionic solution depends on .
(a) temperature
(b) distance between electrodes
(c) concentration of electrolytes in solution
(d) surface area of electrodes

Q 35.

Assertion (A): E , increases with increase in concentration of  Ag+ ions.
Ag /  Ag+
Reason (R): E + has a positive value.
Ag /Ag

Q 36.

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

Q 37.

In the button cells widely used in watches and other devices the following reaction takes place:
ncert-solutions-for-class-12-chemistry-electrochemistry-9

Q 38.

Which of the following statements is correct?
ncert-exemplar-problems-class-12-chemistry-electrochemistry-6

Q 39.

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

Q 40.

How much electricity is required in coulomb for the oxidation of (i) 1 mol of H2O to 02 (ii) 1 mol of FeO to Fe203

Q 41.

The quantity of charge required to obtain one mole of aluminium from

Al2O3 is  (a) IF (b) 6F (c) 3F (d) 2F

Q 42.

Conductivity of an electrolytic solution depends on
(b) concentration of electrolyte
(d) distance between the electrodes

Q 43.

ncert-exemplar-problems-class-12-chemistry-electrochemistry-27

Q 44.

Can ncert-exemplar-problems-class-12-chemistry-electrochemistry-34for cell reaction ever be equal to zero?

Q 45.

Solutions of two electrolytes 'A' and 'B' are diluted. The Am of 'B' increases 1.5 times while that of A increases 25 times. Which of the two is a strong electrolyte? Justify your answer.

Q 46.

Match the terms given in Column 1 with the units given in Column II.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-48

Q 47.

Assertion (A): For measuring resistance of an ionic solution an AC source is used.
Reason (R): Concentration of ionic solution will change if DC source is used.

Q 48.

Assertion (A): Current stops flowing when  Ecell = 0.
Reason (R): Equilibrium of the cell reaction is attained.

Q 49.

How would you determine the standard electrode potential of the system Mg2+1  Mg?

Q 50.

Using the data given in Q. 8, find out in which option the order of reducing power is correct.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-11