CBSE Class 12 Chemistry Electrochemistry MCQs Set E

Question. At 25 °C molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 ohm^–1 cm² mol^–1 and at infinite dilution its molar conductance is 238 ohm^–1 cm² mol^–1. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is
(a) 4.008%
(b) 40.800%
(c) 2.080%
(d) 20.800%

Answer : A

Question. Limiting molar conductivity of NH₄OH [i.e., L°m(NH₄OH)] is equal to
(a) L°m(NH₄Cl) + L°m(NaCl) – L°m(NaOH)
(b) L°m(NaOH) + L°m(NaCl) – L°m(NH₄Cl)
(c) L°m(NH₄OH) + L°m(NH₄Cl) – L°m(HCl)
(d) L°m(NH4Cl) + L°m(NaOH) – L°m(NaCl)

Answer : D

Question. The oxidation potential values of A, B, C and D are – 0.03, + 0.108 V, – 0.07 Vand + 0.1 V respectively. The non-spontaneous cell reaction takes place between
(a) A and B
(b) B and D
(c) D and A
(d) B and C

Answer : A

Question. Calculate the equilibrium constant for the reaction, at 25°C 
Cu(s) + 2Ag⁺ (aq) → Cu²⁺ (aq) + 2Ag(s)
at 25°C, E°_cell = 0.47V, R = 8.314 JK^-1 F = 96500 C is
(a) 1.8 x10¹⁵
(b) 8.5 x10¹⁵
(c) 1.8 x 10¹⁰
(d) 85 x 10¹⁵

Answer : B

Question. The metal used to recover copper from a solution of CuSO4 is
(a) Fe
(b) He
(c) Na
(d) Ag

Answer : A

Question. The standard electrode potential is measured by
(a) electrometer
(b) voltmeter
(c) pyrometer
(d) galvanometer

Answer : B

Question. The standard electrode potentials of Ag⁺/ Ag is + 0. 80V and Cu₊ /Cu is + 0. 34 V. These electrodes are connected through a salt bridge and if
(a) copper electrode acts as a cathode, then E°_cell is + 0.46V.
(b) silver electrode acts as anode, then E°_cell is – 0.34 V
(c) copper electrode acts as anode, then E°_cell is + 0.46V
(d) silver electrode acts as a cathode, then E°_cell is – 0.34 V

Answer : C

Question. Which of the following expression is correct?
(a) ΔG0 = – nFE°_cell
(b) ΔGo = + nFE°_cell
(c) ΔG0 = – 2.303RT nFE°_cell
(d) ΔG0 = – nF log K_c

Answer : A

Question. The standard reduction potential of Zn and Ag in water at 298 K are, Zn²⁺ + 2e^– ⇌ Zn; E° = – 0.76 V and Ag⁺ + e^– ⇌ Ag; E° = + 0.80V. Which of the following reactions take place? 
(a) Zn²⁺ (aq) + 2Ag(s) → 2Ag⁺ (aq) + Zn(s)
(b) Zn(s) + 2Ag⁺ (aq) → Zn²⁺ (aq) + 2Ag(s)
(c) Zn²⁺ (aq) + Ag⁺ (aq) → Zn(s) + Ag(s)
(d) Zn(s) + Ag(s) → Zn²⁺ (aq) + Ag⁺ (aq)

Answer : B

Question. For cell reaction, Zn + Cu²⁺ → Zn²⁺ + Cu cell representation is
(a) Zn l Zn²⁺ ll Cu²⁺ l Cu
(b) Cu l Cu²⁺ ll Zn²⁺ l Zn
(c) Cu l Zn²⁺ ll Zn l Cu²⁺
(d) Cu²⁺ I Zn ll Zn²⁺ l Cu

Answer : A

Question. A current strength of 9.65 amperes is passed through excess fused AlCl₃ for 5 hours. How many litres of chlorine will be liberated at STP? (F = 96500 C)
(a) 2.016
(b) 1.008
(c) 11.2
(d) 20.16

Answer : D

Question. Which one of the following cells can convert chemical energy of H₂ and O₂ directly into electrical energy?
(a) Mercury cell
(b) Daniell cell
(c) Fuel cell
(d) Lead storage cell

Answer : C

Question. Hydrogen-Oxygen fuel cells are used in space craft to supply
(a) power for heat and light
(b) power for pressure
(c) oxygen
(d) water

Answer : B

Question. Prevention of corrosion of iron by zinc coating is called
(a) electrolysis
(b) photoelectrolysis
(c) cathodic protection
(d) galvanization

Answer : D

Question. Which of the following pair(s) is/are incorrectly matched?
(i) R (resistance) – ohm (Ω)
(ii) Ρ (resistivity) – ohm metre (Ωm)
(iii) G (conductance) – seimens or ohm (S)
(iv) k (conductivity) – seimens metre^–1 (Sm^–1)
(a) (i), (ii) and (iii)
(b) (ii) and (iii)
(c) (i), (ii) and (iv)
(d) (iii) only

Answer : C

Question. The best way to prevent rusting of iron is
(a) making it cathode
(b) putting in saline water
(c) Both of these
(d) None of these

Answer : A

Question. Among the following cells:
Leclanche cell (i)
Nickel-Cadmium cell (ii)
Lead storage battery (iii)
Mercury cell (iv)
primary cells are
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i) and (iv)

Answer : D

Question. In electrolysis of dilute H2SO4 using platinum electrodes
(a) H2 is evolved at cathode
(b) NH2 is produced at anode
(c) Cl2 is obtained at cathode
(d) O2 is produced

Answer : A

Question. Which of the following metals is not produced by electrochemical reduction?
(a) Na
(b) Fe
(c) Mg
(d) Al

Answer : B

Question. In the electrolytic cell, flow of electrons is from
(a) cathode to anode in solution
(b) cathode to anode through external supply
(c) cathode to anode through internal supply
(d) anode to cathode through internal supply

Answer : D

Question. Which of the following is a merit of Ni–Cd cell over lead storage battery?
(a) Ni–Cd cell can be re-used.
(b) Ni–Cd cell is comparatively economical to manufacture
(c) Ni–Cd cell has comparatively longer life
(d) All the above are the merits of Ni–Cd cell over lead storage battery.

Answer : C

Question. Electrolysis of a salt solution was carried out, after some time solution turned yellow than salt can be
(i) NaCl (ii) KCl
(iii) RbCl (iv) KBr
(a) (i), (ii) and (iii)
(b) (ii), (ii) and (iv)
(c) (i), (ii) and (iv)
(d) (i), (iii) and (iv)

Answer : A

Question. Which of the following represents variation of molar conductance of electrolyte with (concentration)½ respectively for weak and strong electrolyte ?

Weak acid Strong acid
(a) (iv) (v)
(b) (ii) (iv)
(c) (i) (ii)
(d) (iii) (ii)

Answer : C

Question. Which of the following statements is incorrect?
(a) Electrodes made up of gold participates in the chemical reaction.
(b) Electrolytic products of NaCl are Na and Cl₂ whereas of aqueous NaCl are NaOH, Cl₂ and H₂.
(c) During electrolysis at cathode, reaction with higher value of E⁺ is preferred.
(d) All of the above statements are incorrect.

Answer : A

Question. During electrolysis of sulphuric acid, which of the following processes is possible at anode?

Answer : B

Question. Choose the correct option based on following statements.
(i) Process A is preferred at higher concentration of sulphuric acid.
(ii) Process B is preferred at higher concentration of sulphuric acid.
(iii) Process A is preferred for dilute sulphuric acid.
(iv) Process B is preferred for dilute sulphuric acid.
(v) Both A and B are equally possible at higher concentration.
(a) (v) and (iii)
(b) (iii) and (ii)
(c) (i) and (iv)
(d) (v) and (iv)

Answer : B

Question. Faraday’s laws of electrolysis will fail when
(a) temperature is increased
(b) inert electrodes are used
(c) a mixture of electrolytes is used
(d) None of these cases

Answer : D

Question. Three faradays electricity was passed through an aqueous solution of iron (II) bromide. The weight of iron metal (at. wt = 65) deposited at the cathode (in gm) is
(a) 56
(b) 84
(c) 112
(d) 168

Answer : B

Question. During the charging of lead storage battery, the reaction at anode is represented by

Answer : B

Question. In a hydrogen-oxygen fuel cell, combustion of hydrogen occurs to
(a) produce high purity water
(b) create potential difference between two electrodes
(c) generate heat
(d) remove adsorbed oxygen from elctrode surfaces

Answer : B

Question. Equivalent conductances of Ba²⁺ and Cl^– ions are 127 and 76 ohm^–1 cm^–1 eq^–1 respectively. Equivalent conductance of BaCl₂ at infinite dilution is
(a) 139.5
(b) 101.5
(c) 203
(d) 279

Answer : A

Question. The specific conductance of a 0.1 N KCl solution at 23°C is 0.012 ohm–1 cm–1. The resistance of cell containing the solution at the same temperature was found to be 55 ohm. The cell constant will be
(a) 0.918 cm^–1
(b) 0.66 cm^–1
(c) 1.142 cm^–1
(d) 1.12 cm^–1 

Answer : B

Question. On heating one end of a piece of a metal, the other end becomes hot because of
(a) energised electrons moving to the other end
(b) minor perturbation in the energy of atoms
(c) resistance of the metal
(d) mobility of atoms in the metal.

Answer : A

Question. On electrolysis of dil. sulphuric acid using platinum (Pt) electrode, the product obtained at anode will be
(a) hydrogen gas
(b) oxygen gas
(c) H₂S gas
(d) SO₂ gas. 

Answer : B

Question. The electrolyte used in Leclanche cell is
(a) paste of KOH and ZnO
(b) 38% solution of H₂SO₄
(c) moist paste of NH₄Cl and ZnCl₂
(d) moist sodium hydroxide

Answer : C

Question. How many moles of Pt may be deposited on the cathode when 0.80 F of electricity is passed through a 1.0 M solution of Pt4+?
(a) 1.0 mol
(b) 0.20 mol
(c) 0.40 mol
(d) 0.80 mol

Answer : B

Question. The correct order of E⁰_{M2+ /M} values with negative sign for the four successive elements Cr, Mn, Fe and Co is
(a) Mn > Cr > Fe > Co
(b) Cr < Fe > Mn > Co
(c) Fe > Mn > Cr > Co
(d) Cr > Mn > Fe > Co

Answer : A

Question. If salt bridge is removed from two half-cells the voltage
(a) drops to zero
(b) does not change
(c) increases gradually
(d) increases rapidly

Answer : A

Question. Consider the following relations for emf of a electrochemical cell:
(i) emf of cell = (Oxidation potential of anode) – (Reduction potential of cathode)
(ii) emf of cell = (Oxidation potential of anode) + (Reduction potential of cathode)
(iii) emf of cell = (Reduction potential of anode) + (Reduction potential of cathode)
(iv) emf of cell = (Oxidation potential of anode) – (Oxidation potential of cathode)
Which of the above relations are correct?
(a) (ii) and (iv)
(b) (iii) and (i)
(c) (i) and (ii)
(d) (iii) and (iv)

Answer : A

Question. Which of the following statements is incorrect?
(a) Both electronic and electrolytic conductance depends on the nature of conducting material.
(b) Both electronic and electrolytic conductance varies similarly with temperature.
(c) Electronic conductance is independent but electrolytic conductance depends on the amount of the conducting substance.
(d) All the above statements are incorrect.

Answer : B

Question. The hydrogen electrode is dipped in a solution of pH 3 at 25°C. The potential would be (the value of 2.303 RT/F is 0.059 V)
(a) 0.177 V
(b) 0.087 V
(c) 0.059 V
(d) – 0.177 V

Answer : D

Question. The standard reduction potential of the reaction,
H₂O + e ^– → 1/2 H₂ + OH at 298 K is
(a) E° = RT/F In K_w
(b) E° = – RT/F In [PH₂ )1/2 [OH^–]
(c) E° =_ RT/F In [PH₂ ]1/2 /[H⁺ ]
(d) E° = – RT/F In K_w

Answer : A

Question. Molar conductivities (L°m) at infinite dilution of NaCl, HCl and CH₃COONa are 126.4, 425.9 and 91.0 S cm² mol^–1 respectively. (L°m) for CH₃COOH will be
(a) 425.5 S cm² mol^–1
(b) 180.5 S cm² mol^–1
(c) 290.8 S cm² mol^–1
(d) 390.5 S cm² mol^–1

Answer : D

Question. An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to
(a) increase in ionic mobility of ions
(b) 100% ionisation of electrolyte at normal dilution
(c) increase in both i.e., number of ions and ionic mobility of ions
(d) increase in number of ions.

Answer : A

Question. The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mho cm2 and at infinite dilution is 400 mho cm2. The dissociation constant of this acid is
(a) 1.25 × 10^–6
(b) 6.25 × 10^–4
(c) 1.25 × 10^–4
(d) 1.25 × 10^–5

Answer : D

Question. Kohlrausch’s law states that at
(a) infinite dilution, each ion makes definite contribution to conductance of an electrolyte whatever be the nature of the other ion of the electrolyte
(b) infinite dilution, each ion makes definite contribution to equivalent conductance of an electrolyte, whatever be the nature of the other ion of the electrolyte
(c) finite dilution, each ion makes definite contribution to equivalent conductance of an electrolyte, whatever be the nature of the other ion of the electrolyte
(d) infinite dilution each ion makes definite contribution to equivalent conductance of an electrolyte depending on the nature of the other ion of the electrolyte.

Answer : A