115 + Interview Questions in ELECTRO CHEMISTRY IN GENERAL AWARENESS Page 3 InterviewSolution

101.	Which of the following is an example of secondary batteries? (a) Mercury button cell (b) Leclanche cell (c) Lead storage battery (d) Daniel cell
Answer» (c) Lead storage battery

Discussion

102.	Which one of the following can act as an inert electrode? (a) Graphite (b) Copper (c) Platinum (d) either a (or) e
Answer» (a) either a (or) c

Discussion

103.	Which one of the following is used as an electrolyte Lead storage battery?(a) PbSO4 (b) H2SO4 (c) CuSO4 (d) HNO3
Answer» H₂SO₄ is used as an electrolyte Lead storage battery.

Discussion

104.	Write the cell reaction which occur in the lead storage battery 1. When the battery is in use, 2. When the battery is charging.
Answer» 1. Pb(s) + PbO₂(s) + 2H₂SO₄ (aq) → 2PbSO₄ (s) + 2H₂O(l) At anode: Pb(s) + SO₄^2- → PbSO₄ (s) + 2e^- At cathod: PbO₄ (s) + SO^2- (aq) + 4H⁺ (aq) + 2e^- → PbSO₄ (s) + 2H₂O(l) 2. 2PbSO₄ (s) + 2H₂O(s) → PbSO₄ (s) + 2H₂SO₄ (aq)

104.

Write the cell reaction which occur in the lead storage battery 1. When the battery is in use, 2. When the battery is charging.

Answer»

1. Pb(s) + PbO₂(s) + 2H₂SO₄ (aq) → 2PbSO₄ (s) + 2H₂O(l)

At anode: Pb(s) + SO₄^2- → PbSO₄ (s) + 2e^-

At cathod: PbO₄ (s) + SO^2- (aq) + 4H⁺ (aq) + 2e^- → PbSO₄ (s) + 2H₂O(l)

2. 2PbSO₄ (s) + 2H₂O(s) → PbSO₄ (s) + 2H₂SO₄ (aq)

Discussion

105.	Assertion(A): As a lead storage battery gets discharged. density of electrolyte present in it decreases. Reason (R): Lead and Lead dioxide both react with sulphuric acid to form lead sulphate. (a) Both A and R are correct (b) A is correct but R is wrong (c) A is wrong but R is correct (d) Both A and R are wrong.
Answer» (a) Both A and R are correct

Discussion

106.	Which of the following is used to calculate the conductivity of strong electrolytes? (a) Kohlraush’s law (b) Henderson equation (c) Debye-Huckel and Onsagar equation (d) Ostwald’s dilution law
Answer» (c) Debye-Huckel and Onsagar equation

Discussion

107.	For strong electrolytes the molar conductivity increases on dilution and reaches a maximum value at infinite dilution. Justify this statement.
Answer» For a strong electrolyte, at high concentration, the number of constituent ions of the electrolyte in a given volume is high and hence the attractive force between the oppositely charged ions is also high. The ions also experienced a viscous drag due to greater solvation. These factors attribute for the low molar conductivity at high concentration. When the dilution increases, the ions are far apart and the attractive forces decreases. At infinite dilution, the ions are so far apart, the interaction between them becomes insignificant and hence the molar conductivity increases and reaches a maximum value at infinite dilution.

107.

For strong electrolytes the molar conductivity increases on dilution and reaches a maximum value at infinite dilution. Justify this statement.

Answer»

For a strong electrolyte, at high concentration, the number of constituent ions of the electrolyte in a given volume is high and hence the attractive force between the oppositely charged ions is also high. The ions also experienced a viscous drag due to greater solvation. These factors attribute for the low molar conductivity at high concentration.

When the dilution increases, the ions are far apart and the attractive forces decreases. At infinite dilution, the ions are so far apart, the interaction between them becomes insignificant and hence the molar conductivity increases and reaches a maximum value at infinite dilution.

Discussion

108.	Explain about Debye-Huckel and Onsagar equation.
Answer» The influence of ion-ion interactions on the conductivity of strong electrolytes was studied by Debye and Huckel. They considered that each ion is surrounded by an ionic atmosphere of opposite sign, and derived an expression relating the molar conductance of strong electrolytes with the concentration by It was further developed by Onsagar. For a uni – univalent electrolyte the Debye Huckel and Onsagar equation is given below. Λ_m = Λ_m° (A + B Λ°m) \(\sqrt{c}\) Where A and B are constants which depend only in the nature of the solvent and temperature.

108.

Explain about Debye-Huckel and Onsagar equation.

Answer»

The influence of ion-ion interactions on the conductivity of strong electrolytes was studied by Debye and Huckel.

They considered that each ion is surrounded by an ionic atmosphere of opposite sign, and derived an expression relating the molar conductance of strong electrolytes with the concentration by It was further developed by Onsagar. For a uni – univalent electrolyte the Debye Huckel and Onsagar equation is given below.

Λ_m = Λ_m° (A + B Λ°m) \(\sqrt{c}\)

Where A and B are constants which depend only in the nature of the solvent and temperature.

Discussion

109.	An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to ………. (a) increase in both the number of ions and ionic mobility of ions (b) increase in number of ions (c) increase in ionic mobility of ions (d) 100% ionization of electrolyte at normal dilution
Answer» (c) increase in ionic mobility of ions

Discussion

110.	Assertion(A): Molar conductance of a solution increases with increase in dilution. Reason (R): For a strong electrolyte, inter ionic forces of attraction decreases with dilution and so conductivity increases. For a weak electrolyte, degree of dissociation increases with dilution and conductivity increases. (a) Both A and R are correct and R is the correct explanation of A . (b) A and R are wrong (c) A is correct but R is not the explanation of A (d) A is wrong but R is correct
Answer» (a) Both A and R are correct and R is the correct explanation of A

Discussion

111.	Why the variations of equivalent conductance on dilution of a strong electrolyte differ from that of a weak electrolyte?
Answer» In strong electrolytes, the increase in equivalent conductance is due to weakening of the ion-ion interaction on dilution which increases ionic mobility as a result of solvation effect. On the other hand in weak electrolytes the increase in equivalent conductance is also due to increases in degree of dissociation of weak electrolyte with dilution.

Discussion

112.	For weak electrolyte, sudden increase In molar conductance with dilution. Prove this statement.
Answer» For a weak electrolyte, at high concentration the plot is almost parallel to concentration axis with slight increase in conductivity as the dilution increases. When the concentration approaches zero, there is a sudden increase in the molar conductance and the curve is almost parallel to Am axis. This is due to the fact that the dissociation of the weak electrolyte increases with the increase in dilution (Ostwald’s dilution law).

Discussion

113.	Which reference electrode is used to measure the electrode potential of other electrodes ?
Answer» Standard hydrogen electrode.

Discussion

114.	Following reactions may occur at cathode during the electrolysis of aqueous CuCl2 solution using Pt electrodes:Cu2+(aq) + 2 e- → Cu(s) :E° = +0.34 VH+(aq) + e- → 1/2H2(g) : E° = 0.00 VOn the basis of their standard electrode potential values, which reaction is feasible at cathode and why ?
Answer» Cu²⁺(aq) + 2 e^- → Cu(s) Becaus.e it has higher reduction potential. Detailed Answer: As reaction with higher value of standard electrode potential occurs at cathode get reduced. So, the reaction occurring at cathode is Cu²⁺(aq) + 2 e^- → Cu(s)

114.

Following reactions may occur at cathode during the electrolysis of aqueous CuCl2 solution using Pt electrodes:Cu2+(aq) + 2 e- → Cu(s) :E° = +0.34 VH+(aq) + e- → 1/2H2(g) : E° = 0.00 VOn the basis of their standard electrode potential values, which reaction is feasible at cathode and why ?

Answer»

Cu²⁺(aq) + 2 e^- → Cu(s)

Becaus.e it has higher reduction potential.

Detailed Answer:

As reaction with higher value of standard electrode potential occurs at cathode get reduced. So, the reaction occurring at cathode is

Cu²⁺(aq) + 2 e^- → Cu(s)

Discussion

115.	Following reactions can occur at cathode during the electrolysis of aqueous silver nitrate solution using Pt electrodes:Ag+(aq) + e- → Ag(s) : E° = 0.80 VH+(aq) + e- → 1/2H2(g) : E° = 0.00 VOn the basis of their standard electrode potential values, which reaction is feasible at cathode and why ?
Answer» Ag⁺(aq) + e^- → Ag(s) Because it has higher reduction potential. Detailed Answer: As reaction with higher value of standard electrode potential occurs at cathode get reduced. So, the reaction occurring at cathode is Ag⁺(aq) + e^- → Ag(s)

115.

Following reactions can occur at cathode during the electrolysis of aqueous silver nitrate solution using Pt electrodes:Ag+(aq) + e- → Ag(s) : E° = 0.80 VH+(aq) + e- → 1/2H2(g) : E° = 0.00 VOn the basis of their standard electrode potential values, which reaction is feasible at cathode and why ?

Answer»

Ag⁺(aq) + e^- → Ag(s)

Because it has higher reduction potential.

Detailed Answer:

As reaction with higher value of standard electrode potential occurs at cathode get reduced. So, the reaction occurring at cathode is

Ag⁺(aq) + e^- → Ag(s)

Discussion

Explore topic-wise InterviewSolutions in .

Which of the following is an example of secondary batteries? (a) Mercury button cell (b) Leclanche cell (c) Lead storage battery (d) Daniel cell

Which one of the following can act as an inert electrode? (a) Graphite (b) Copper (c) Platinum (d) either a (or) e

Which one of the following is used as an electrolyte Lead storage battery?(a) PbSO4 (b) H2SO4 (c) CuSO4 (d) HNO3

Write the cell reaction which occur in the lead storage battery 1. When the battery is in use, 2. When the battery is charging.

Which of the following is used to calculate the conductivity of strong electrolytes? (a) Kohlraush’s law (b) Henderson equation (c) Debye-Huckel and Onsagar equation (d) Ostwald’s dilution law

For strong electrolytes the molar conductivity increases on dilution and reaches a maximum value at infinite dilution. Justify this statement.

Explain about Debye-Huckel and Onsagar equation.

An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to ………. (a) increase in both the number of ions and ionic mobility of ions (b) increase in number of ions (c) increase in ionic mobility of ions (d) 100% ionization of electrolyte at normal dilution

Why the variations of equivalent conductance on dilution of a strong electrolyte differ from that of a weak electrolyte?

For weak electrolyte, sudden increase In molar conductance with dilution. Prove this statement.

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

Following reactions may occur at cathode during the electrolysis of aqueous CuCl2 solution using Pt electrodes:Cu2+(aq) + 2 e- → Cu(s) :E° = +0.34 VH+(aq) + e- → 1/2H2(g) : E° = 0.00 VOn the basis of their standard electrode potential values, which reaction is feasible at cathode and why ?