CBSE Class 12 Chemistry Electrochemistry MCQs Set 06

Question. In the electrochemical reaction
2Fe³⁺ Zn → Zn²⁺ + 2Fe²⁺ ,on increasing the concentration of Fe²⁺
(a) increases cell emf
(b) increases the current flow
(c) decreases the cell emf
(d) alters the pH of the solution
Answer: c

 Question. If 0.01 M solution of an electrolyte has a resistance of 40 ohms in a cell having a cell constant of 0.4 cm^–1, then its molar conductance in ohm^–1 cm² mol^–1 is
(a) 10²
(b) 104
(c) 10
(d) 10³
Answer: d

Question. Which of the following solutions of KCl will have the highest value of specific conductance?
(a) 1.0 N
(b) 0.1 N
(c) 1.0 ×10^–2N
(d) 1.0 ×10^–3N
Answer: a

Question. In the cell reaction
Cu(s) + 2Ag+ (aq) → Cu²⁺ (aq) + 2Ag(s) ,
E^o_cell = 0.46 V. By doubling the concentration of Cu²⁺, Eocell will become
(a) doubled
(b) halved
(c) increases but less than double
(d) decreases by a small fraction
Answer: d

Question. The unit of equivalent conductivity is
(a) ohm cm
(b) ohm^–1 cm² (g equivalent)^–1
(c) ohm cm² (g equivalent)
(d) S cm^–2
Answer: b

Question. For the galvanic cell
Zn | Zn²⁺ (0.1M) || Cu²⁺ (1.0M)|Cu the cell potential increase if:
(a) [Zn²⁺] is increased
(b) [Cu²⁺] is increased
(c) [Cu²⁺] is decreased
(d) surface area of anode is increased
Answer: b

Question. Consider the following cell reaction:
2Fe(s) + O₂(g) + 4H⁺ (aq) → 2Fe²⁺ (aq) + 2H₂O(l);E 1.67V 
At [Fe²⁺] = 10^–3 M, p(O₂) = 0.1 atm and pH = 3, the cell potential at 25ºC is
(a) 1.47 V
(b) 1.77 V
(c) 1.87 V
(d) 1.57 V
Answer: d

 Question. Which of the following statement is not correct about an inert electrode in a cell ?
(a) It does not participate in the cell reaction.
(b) It provides surface either for oxidation or for reduction reaction.
(c) It provides surface for conduction of electrons.
(d) It provides surface for redox reaction.
Answer: d

Question. A button cell used in watches functions as following
Zn(s) + Ag₂O(s) + H₂O(l) ⇌ 2Ag(s) + Zn²⁺(aq) + 2OH^–(aq)
If half cell potentials are :
Zn²⁺(aq) + 2e^– → Zn(s); Eo = – 0.76 V
Ag₂O(s) + H₂O (l) + 2e^– → 2Ag(s) + 2OH^–(aq); Eo = 0.34 V
The cell potential will be :
(a) 0.42 V
(b) 0.84 V
(c) 1.34 V
(d) 1.10 V
Answer: d

Question. Standard reduction potentials of the half reactions are given below :
F₂(g) + 2e^– → 2F^– (aq); E° = + 2.85 V
Cl₂(g) + 2e^– → 2Cl^–(aq); E° = + 1.36 V
Br₂(l) + 2e^– → 2Br^–(aq); E° = + 1.06 V
I₂(s) + 2e^– → 2I^–(aq); E° = + 0.53 V
The strongest oxidising and reducing agents respectively are
(a) F₂ and I^–
(b) Br₂ and Cl^–
(c) Cl₂ and Br^–
(d) Cl₂ and I₂
Answer: a

Question. On the basis of the following E° values, the strongest oxidizing agent is :
[Fe(CN)₆]^4– →[Fe(CN)₆]^3– + e^– ; E° = – 0.35 V
Fe²⁺ → Fe³⁺ + e–; E° = – 0.77 V
(a) [Fe(CN)₆]^4–
(b) Fe²⁺
(c) Fe³⁺
(d) [Fe(CN)₆]^3–
Answer: c

Question. The oxidation potentials of A and B are +2.37 and +1.66 V respectively. In chemical reactions
(a) A will be replaced by B
(b) A will replace B
(c) A will not replace B
(d) A and B will not replace each other
Answer: b

Question. Standard electrode potential of three metals X, Y and Z are – 1.2 V, + 0.5 V and – 3.0 V, respectively. The reducing power of these metals will be :
(a) Y > Z > X
(b) X > Y > Z
(c) Z > X > Y
(d) X > Y > Z
Answer: c

Question. The standard e.m.f. of a galvanic cell involving cell reaction with n = 2 is found to be 0.295 V at 25°C. The equilibrium constant of the reaction would be
(Given F = 96500 C mol–1; R = 8.314JK^–1mol^–1)
(a) 2.0×10¹¹
(b) 4.0×10¹²
(c) 1.0×10²
(d) 1.0×10¹⁰
Answer: d

Question. The specific conductance of a 0.1 N KCl solution at 23°C is 0.012 ohm^–1cm^–1. The resistance of cell containing the solution at the same temperature was found to be 55 ohm.The cell constant will be
(a) 0.142 cm^–1
(b) 0.66 cm^–1
(c) 0.918 cm^–1
(d) 1.12 cm^–1
Answer: b

 Question. Which of the following statements about galvanic cell is incorrect
(a) anode is positive
(b) oxidation occurs at the electrode with lower reduction potential
(c) cathode is positive
(d) reduction occurs at cathode
Answer: a

Question. Which cell will measure standard electrode potential of copper electrode ?
(a) Pt (s) |H₂ (g, 0.1 bar) |H⁺ (aq., 1 M) ||Cu²⁺ (aq., 1 M) | Cu
(b) Pt (s) |H₂ (g, 1 bar) |H⁺ (aq., 1 M) ||Cu²⁺ (aq., 2 M) | Cu
(c) Pt (s) |H₂ (g, 1 bar) |H⁺ (aq., 1 M) ||Cu²⁺ (aq., 1 M) | Cu
(d) Pt (s) |H₂ (g, 1 bar) |H⁺ (aq., 0.1 M) ||Cu²⁺ (aq., 1 M) | Cu
Answer: c

Question. Without losing its concentration ZnCl₂ solution cannot be kept in contact with
(a) Au
(b) Al
(c) Pb
(d) Ag
Answer: b

Question. Zn (s) | Zn ²⁺ (aq) | | Cu ²⁺ (aq) |Cu(s) is
anode cathode
(a) Weston cell
(b) Daniel cell
(c) Calomel cell
(d) Faraday cell
Answer: b

Question. The electrode potential E (Zn²⁺/Zn) of a zinc electrode at 25°C with an aqueous solution of 0.1 M ZnSO₄ is [E⁰ _(Zn²⁺/Zn)= –0.76 V. Assume 2.303RT/F = 0.06 at 298 K].
(a) + 0.73
(b) – 0.79
(c) – 0.82
(d) – 0.70
Answer: b

Question. Specific conductance of a 0.1 N KCl solution at 23ºC is 0.012 ohm^–1 cm^–1. Resistance of cell containing the solution at same temperature was found to be 55 ohm. The cell constant is
(a) 0.0616 cm^–1
(b) 0.66 cm^–1
(c) 6.60 cm^–1
(d) 660 cm^–1
Answer: b

Question. E° for the cell,
Zn | Zn²⁺ (aq) | | Cu²⁺ (aq)| Cu is 1.10 V at 25°C. The equilibrium constant for the cell reaction
Zn + Cu²⁺ (aq) ⇌ Cu+ Zn²⁺ (aq) is of the order of
(a) 10^–37
(b) 10³⁷
(c) 10^–17
(d) 10¹⁷
Answer: b

Question. What is the standard cell potential E° for an electrochemical cell in which the following reaction takes place spontaneously ?
Cl₂(g) + 2Br^– → Br₂(aq)+ 2Cl^– ΔG°=-50.6 kJ
(a) 1.2 V
(b) 0.53 V
(c) 0.26 V
(d) –0.53 V
Answer: c

Question. In which of the following conditions salt bridge is not required in a galvanic cell?
(a) When galvanic cell is used in geyser.
(b) When distance between oxidation half cell and reduction half cell is negligible.
(c) Electrolytic solutions used in both the half cells are of same concentration.
(d) When both the electrodes are dipped in the same electrolytic solution.
Answer: d

Question. The unit of specific conductivity is
(a) ohm cm^–1
(b) ohm cm^–2
(c) ohm^–1 cm
(d) ohm^–1 cm^–1
Answer: d

Question. The standard emf of a cell, involving one electron change is found to be 0.591 V at 25°C. The equilibrium constant of the reaction is (F = 96500 C mol^–1)
(a) 1.0 × 10¹
(b) 1.0 × 10⁵
(c) 1.0 × 10¹⁰
(d) 1.0 ×10³⁰
Answer: c

Question. Standard electrode potential for Sn⁴⁺ / Sn²⁺ couple is + 0.15 V and that for the Cr³⁺ / Cr couple is – 0.74 V. These two couples in their standard state are connected to make a cell. The cell potential will be
(a) + 1.19 V
(b) + 0.89 V
(c) + 0.18 V
(d) + 1.83 V
Answer: b

Question. Specific conductance of 0.1 M HNO₃ is 6.3×10^–2 ohm^–1 cm^–1.The molar conductance of the solution is
(a) 100 ohm^–1 m²
(b) 515 ohm^–1 cm²
(c) 630 ohm^–1 cm²
(d) 6300 ohm^–1 cm²
Answer: c

 Question. The standard hydrogen electrode potential is zero, because
(a) hydrogen oxidized easily
(b) electrode potential is considered as zero
(c) hydrogen atom has only one electron
(d) hydrogen is a very light element
Answer: b

 Question. Which of the following statements is incorrect regarding electrochemistry?
(a) It is the study of production of electricity from energy released during spontaneous chemical reactions.
(b) NaOH, Cl_2, alkali and alkaline earth metals are prepared by electrochemical methods.
(c) The demerit associated with electrochemical methods is that they are more polluting. Thus they are ecodestructive.
(d) Electrochemical reactions are more energy efficient and less polluting.
Answer: c

Question. A smuggler could not carry gold by depositing iron on the gold surface since
(a) gold is denser
(b) iron rusts
(c) gold has higher reduction potential than iron
(d) gold has lower reduction potential than iron 
Answer: c

Question. The tendency of an electrode to lose electrons is known as
(a) electrode potential
(b) reduction potential
(c) oxidation potential
(d) e.m.f.
Answer: c

Question. What flows in the internal circuit of a galvanic cell?
(a) Ions
(b) Electrons
(c) Electricity
(d) Atoms
Answer: a

Question.The cell constant of a conductivity cell ___________.
(a) changes with change of electrolyte.
(b) changes with change of concentration of electrolyte.
(c) changes with temperature of electrolyte.
(d) remains constant for a cell. 
Answer: d

Question. The value of electrode potential (10^–4 M) H+ | H₂(1 atm) | Pt at 298 K would be
(a) – 0.236 V
(b) + 0.404 V
(c) + 0.236 V
(d) – 0.476 V
Answer: a

 Question. Given that the standard reduction potentials for M+/M and N+/N electrodes at 298 K are 0.52 V and 0.25 V respectively.Which of the following is correct in respect of the following electrochemical cell ?
M/M⁺ | | N⁺/N
(a) The overall cell reaction is a spontaneous reaction.
(b) The standard EMF of the cell is – 0.27 V.
(c) The standard EMF of the cell is 0.77 V.
(d) The standard EMF of the cell is – 0.77 V.
Answer: b

Question. The cell reaction Cu + 2Ag⁺ → Cu⁺² + Ag is best represented by
(a) Cu(s) | Cu⁺² (aq) | |Ag⁺ (aq) |Ag(s)
(b) Pt | Cu⁺² || Ag⁺ (aq) | Ag(s)
(c) Cu⁺² | Cu | | Pt | Ag
(d) None of the above representations
Answer: a

 Question. The chemical reaction,
2AgCl(s) + H₂ (g) → 2HCl(aq) + 2Ag(s) taking place in a galvanic cell is represented by the notation
(a) Pt(s) | H₂ (g),1 bar |1MKCl(aq) | AgCl(s) | Ag(s)
(b) Pt(s) | H₂(g),1 bar |1MHCl(aq) |1MAg⁺ (aq) | Ag(s)
(c) Pt(s) |H₂ (g),1 bar |1MHCl(aq) | AgCl(s) |Ag(s)
(d) Pt(s) |H₂ (g),1 bar |1MHCl(aq) | Ag(s) |AgCl(s)
Answer: b

Question.The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called _________.
(a) Cell potentials
(b) Cell emf
(c) Potential difference
(d) Cell voltage
Answer: b

Question. Which device converts chemical energy of a spontaneous redox reaction into electrical energy?
(a) Galvanic cell
(b) Electrolytic cell
(c) Daniell cell
(d) Both (a) and (c)
Answer: d

Question. The reference electrode is made by using
(a) ZnCl₂
(b) CuSO₄
(c) HgCl₂
(d) Hg₂Cl₂ 
Answer: d

Question. The resistance of 0.01 N solution of an electrolyte was found to be 220 ohm at 298 K using a conductivity cell with a cell constant of 0.88cm^–1. The value of equivalent conductance of solution is –
(a) 400 mho cm² g eq^–1
(b) 295 mho cm² g eq^–1
(c) 419 mho cm² g eq^–1
(d) 425 mho cmm² g eq^–1
Answer: a