Chemistry

Electrochemistry

Question:

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

Answer:

(a, b) Conductivity of electrolyte solution is due to presence of mobile ions in the solution. This type of conductance is known as ionic conductance. Conductivity of these type of solutions depend upon
(i) the nature of electrolyte added
(ii) size of the ion produced and their solvation
(iii) concentration of electrolyte
(iv) nature of solvent and its viscosity
(v) temperature
While power of source or distance between electrodes has no effect on conductivity of electrolyte solution.
Hence, options (a) and (b) are the correct choices.

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Electrochemistry

Q 1.

Use the data given in Q. 8 and find out the most stable ion in its reduced form.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-13

Q 2.

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

Q 3.

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 Mn04- to Mn2+?

Q 4.

The positive value of the standard electrode potential of Cu+2/Cu indicates that
(a) this redox couple is a stronger reduction agent than the H/H2  couple
(b) this redox couple is a stronger oxidizing agent than H+/H2
(c) Cu can displace  H2 from acid
(d) Cu cannot displace  H2   from acid

Q 5.

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

Q 6.

Three electrolytic cells A, B, C containing solutions of ZnS04, AgNO3 and CuS04, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 45 g of silver deposited at the cathode of call B. How long did the current flow? What mass of copper and zinc were deposited?

Q 7.

E °en = 1.1 V for Daniell cell. Which of the following expressions are correct description of state of equilibrium in this cell?
ncert-exemplar-problems-class-12-chemistry-electrochemistry-25

Q 8.

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

Q 9.

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

Q 10.

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

Q 11.

Match the terms given in Column I with the items given in Column II.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-49

Q 12.

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

Q 13.

Consider the figure given below and answer the questions (i) to (vi) that follow.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-57
(i) Redraw the diagram to show the direction of electron flow.
(ii) Is silver plate anode or cathode?
(iii)What will happen if salt bridge is removed?
(iv)When will the cell stop functioning?
(v)How will concentration of Zn+2  cell functions?
(vi)How will the concentration of Zn+2 ions and Ag+ ions be affected after the cell becomes ‘dead'?

Q 14.

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 15.

The cell in which the following reaction 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 16.

Write the Nemst equation for the cell reaction in the Daniell cell. How will the Ecell be affected when concentration of Zn2+ ions is increased?

Q 17.

Which reference electrode is used to measure the electrode potential of other electrodes?

Q 18.

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 19.

ncert-exemplar-problems-class-12-chemistry-electrochemistry-18

Q 20.

Predict if the reaction between the following is feasible:
ncert-solutions-for-class-12-chemistry-electrochemistry-21
ncert-solutions-for-class-12-chemistry-electrochemistry-22

Q 21.

Given the standard electrode potentials, K+/K=-2. 93 V, Ag+/Ag = 0.80 V, Hg2+/Hg =0.79V, Mg2+/Mg=-2.37V, Cr3+/Cr=0.74V.
Arrange these metals in their increasing order of reducing power.

Q 22.

Use the data given in Q. 8 and find out which of the following is the strongest oxidizing agent.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-9

Q 23.

How will the pH of brine (aq. NaCl solution) be affected when it is electrolysed?

Q 24.

In an aqueous solution, how does specific conductivity of electrolytes change with addition of water?

Q 25.

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 26.

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

Al2O3 is  (a) IF (b) 6F (c) 3F (d) 2F

Q 27.

Conductivity K, is equal to
ncert-exemplar-problems-class-12-chemistry-electrochemistry-31

Q 28.

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 29.

Why is alternating current used for measuring resistance of an electrolytic solution?

Q 30.

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 31.

Match the items of Column I and Column II.
ncert-exemplar-problems-class-12-chemistry-electrochemistry-52

Q 32.

In the electrolysis of aqueous sodium chloride solution, which of the half-cell reaction will occur at anode?
ncert-exemplar-problems-class-12-chemistry-electrochemistry-20

Q 33.

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

Q 34.

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 35.

What is the relationship between Gibbs free energy of the cell reaction in a galvanic cell and the emf of the cell? When will the maximum work be obtained from a galvanic cell?

Q 36.

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

Q 37.

A solution of Ni(N03)2 is electrolyzed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

Q 38.

What does the negative sign in the expression ncert-exemplar-problems-class-12-chemistry-electrochemistry-38 mean? Zn /Zn

Q 39.

What is electrode potential?

Q 40.

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

Q 41.

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

Q 42.

Match the items of Column I and Column II on the basis of data given below:
ncert-exemplar-problems-class-12-chemistry-electrochemistry-53

Q 43.

Assertion (A): Electrolysis of NaCl solution gives chlorine at anode instead of 02.
Reason (R): Formation of oxygen at anode requires overvoltage.

Q 44.

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

Q 45.

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

Q 46.

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

Q 47.

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 48.

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 49.

A galvanic cell has electrical potential of 1.1 V. If an opposing potential of 1.1 V is applied to this cell, what will happen to the cell reaction and current flowing through the cell?

Q 50.

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