Class 12 Chemistry Chapter 3 Electrochemistry MCQ Question with Answers

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Electrochemistry Class 12 MCQ with Answers

Class 12 Chemistry MCQ with answers are given here to chapter Electrochemistry. These MCQs are based on the latest CBSE board syllabus and relate to the latest Class 12 Chemistry syllabus. By Solving these Class 12 MCQs, you will be able to analyze all of the concepts quickly in the chapter and get ready for the Class 12 Annual exam.

Learn Class 12 Electrochemistry MCQ with answers pdf free download according to the latest CBSE and NCERT syllabus. Students should prepare for the examination by solving Electrochemistry Class 12 MCQ with answers given below.

Question 1. Standard reduction potentials of the half reactions are given below :
F_2(g) + 2e^– → 2F–_(aq) ; E° = + 2.85 V
Cl_2(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

Question 2. The standard electrode potential (E°) values of Al³⁺/Al, Ag⁺/Ag, K⁺/K and Cr³⁺/Cr are –1.66 V, 0.80 V, –2.93 V and –0.74 V, respectively. The correct decreasing order of reducing power of the metal is
(a) Ag > Cr > Al > K
(b) K > Al > Cr > Ag
(c) K > Al > Ag > Cr
(d) Al > K > Ag > Cr

Question 3. A button cell used in watches function as following :
Zn_(s) + Ag₂O(s) + H₂O(l) ⇌ 2Ag(s) + Zn²⁺_(aq) + 2OH^–_(aq)
If half cell potentials are
Zn²⁺_(aq) + 2e^– → Zn(s); E° = – 0.76 V
Ag₂O_(s) + H₂O(l) + 2e^– → 2Ag_(s) + 2OH–(aq); E° = 0.34 V
The cell potential will be
(a) 0.84 V
(b) 1.34 V
(c) 1.10 V
(d) 0.42 V 

Question 4. 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

Question 5. A solution contains Fe²⁺, Fe³⁺ and I– ions. This solution was treated with iodine at 35°C. E° for Fe³⁺/Fe²⁺ is + 0.77 V and E° for I₂/2I– = 0.536 V. The favourable redox reaction is
(a) I₂ will be reduced to I–
(b) there will be no redox reaction
(c) I^– will be oxidised to I₂
(d) Fe²⁺ will be oxidised to Fe³⁺. 

Question 6. Standard electrode potentials 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) Y > X > Z
(c) Z > X > Y
(d) X > Y > Z 

Question 7. A hypothetical electrochemical cell is shown below : A/ A+ (x M)||B+(y M)|B
The emf measured is + 0.20 V. The cell reaction is
(a) A + B⁺ → A+ + B
(b) A⁺ + B → A + B+
(c) A⁺ + e– → A; B⁺ + e^– → B
(d) the cell reaction cannot be predicted. 

Question 8. Consider the following relations for emf of an 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 = (Reductional 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) (iii) and (i)
(b) (i) and (ii)
(c) (iii) and (iv)
(d) (ii) and (iv)

Question 9. 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) Fe³⁺
(b) [Fe(CN)₆]^3–
(c) [Fe(CN)₆]^4–
(d) Fe²⁺ 

Question 10. Standard electrode potentials are Fe2+/Fe;
E° = –0.44 and Fe³⁺/Fe²⁺; E° = 0.77. Fe²⁺, Fe³⁺ and Fe blocks are kept together, then
(a) Fe³⁺ increases
(b) Fe3+ decreases
(c) Fe²⁺/Fe³⁺ remains unchanged
(d) Fe²⁺ decreases. 

Question 11. E°Fe²⁺/Fe = – 0.441 V and E°Fe³⁺/Fe²⁺ = 0.771 V, the standard EMF of the reaction Fe + 2Fe³⁺ → 3Fe²⁺ will be
(a) 0.111 V
(b) 0.330 V
(c) 1.653 V
(d) 1.212 V 

Question 12. Standard reduction potentials at 25°C of Li+|Li, Ba²⁺|Ba, Na⁺|Na and Mg²⁺|Mg are –3.05, –2.90,–2.71 and –2.37 volt respectively. Which one of the following is the strongest oxidising agent?
(a) Ba²⁺
(b) Mg²⁺
(c) Na⁺
(d) Li⁺ 

Question 13. Electrode potential for the following half-cell reactions are
Zn → Zn²⁺ + 2e–; E° = + 0.76 V;
Fe → Fe2+ + 2e–; E° = + 0.44 V.
The EMF for the cell reaction
Fe²⁺ + Zn → Zn²⁺ + Fe will be
(a) – 0.32 V
(b) + 1.20 V
(c) – 1.20 V
(d) + 0.32 V

Question 14. An electrochemical cell is set up as :
Pt; H₂ (1 atm)|HCl(0.1 M) || CH₃COOH (0.1 M) |H₂ (1 atm); Pt. The e.m.f. of this cell will not be zero, because
(a) acids used in two compartments are different
(b) e.m.f. depends on molarities of acids used
(c) the temperature is constant
(d) pH of 0.1 M HCl and 0.1 M CH₃COOH is not same. 

Question 15. For the cell reaction :
2Fe³⁺_(aq) + 2I–(aq) 2Fe²⁺_(aq) + I_2(aq)
E°_cell = 0.24 V at 298 K. The standard Gibbs’ energy (ΔrG°)of the cell reaction is
[Given that Faraday constant, F = 96500 C mol^–1]
(a) 23.16 kJ mol^–1
(b) –46.32 kJ mol^–1
(c) –23.16 kJ mol^–1
(d) 46.32 kJ mol^–1

Question 16. In the electrochemical cell :
Zn|ZnSO₄₍0.01 M)||CuSO₄(1.0 M)|Cu, the emf of this Daniell cell is E1. When the concentration of ZnSO₄ is changed to 1.0 M and that of CuSO4 changed to 0.01 M, the emf changes to E₂.
From the followings, which one is the relationship between E₁ and E₂? (Given, RT/F = 0.059)
(a) E₁ < E₂
(b) E₁ > E₂
(c) E₂ = 0 ≠ E₁
(d) E₁ = E₂

Question 17. A solution of potassium bromide is treated with each of the following. Which one would liberate bromine?
(a) Hydrogen iodide
(b) Sulphur dioxide
(c) Chlorine
(d) Iodine

Question 18. A hydrogen gas electrode is made by dipping  platinum wire in a solution of HCl of pH = 10 and by passing hydrogen gas around the platinum wire at one atm pressure. The oxidation potential of electrode would be
(a) 0.118 V
(b) 1.18 V
(c) 0.059 V
(d) 0.59 V 

Question 19. If the E°cell for a given reaction has a negative value,which of the following gives the correct relationships for the values of ΔG° and Keq ?
(a) ΔG° > 0; K_eq < 1
(b) ΔG° > 0; K_eq > 1
(c) ΔG° < 0; K_eq > 1
(d) ΔG° < 0; K_eq < 1

Question 20. The pressure of H₂ required to make the potential of H₂ electrode zero in pure water at 298 K is
(a) 10^–10 atm
(b) 10^–4 atm
(c) 10^–14 atm
(d) 10^–12 atm.

Question 21. For the reduction of silver ions with copper metal, the standard cell potential was found to be + 0.46 V at 25 °C. The value of standard Gibbs energy, DG°
will be (F = 96500 C mol^–1)
(a) – 89.0 kJ
(b) – 89.0 J
(c) – 44.5 kJ
(d) – 98.0 kJ 

Question 22. Given :
(i) Cu²⁺ + 2e– → Cu, E° = 0.337 V
(ii) Cu²⁺ + e– → Cu+, E° = 0.153 V
Electrode potential, E° for the reaction,
Cu⁺ + e– → Cu, will be
(a) 0.90 V
(b) 0.30 V
(c) 0.38 V
(d) 0.52 V 

Question 23. Consider the half-cell reduction reaction
Mn²⁺ + 2e– → Mn, E° = – 1.18 V
Mn²⁺ → Mn³⁺ + e–, E° = – 1.51 V
The E° for the reaction, 3Mn²⁺ → Mn0 + 2Mn³⁺, and possibility of the forward reaction are respectively
(a) – 4.18 V and yes
(b) + 0.33 V and yes
(c) + 2.69 V and no
(d) – 2.69 V and no.

Question 24. The equilibrium constant of the reaction :
Cu(s) + 2Ag⁺_(aq) → Cu²⁺(aq) + 2Ag(s);
E° = 0.46 V at 298 K is
(a) 2.0 × 10¹⁰
(b) 4.0 × 10¹⁰
(c) 4.0 × 10¹⁵
(d) 2.4 × 10¹⁰ 

Question 25. 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 = 8.314 J K^–1 mol^–1)
(a) 2.0 × 10¹¹
(b) 4.0 × 10¹²
(c) 1.0 × 10²
(d) 1.0 × 10¹⁰

Question 26. Standard free energies of formation (in kJ/mol) at 298 K are –237.2, –394.4 and –8.2 for H₂O(l), CO₂(g) and pentane(g) respectively. The value of E°cell for the pentane-oxygen fuel cell is
(a) 1.0968 V
(b) 0.0968 V
(c) 1.968 V
(d) 2.0968 V 

Question 27. For the disproportionation of copper
2Cu⁺ → Cu²⁺ + Cu, E° is (Given : E° for Cu²⁺/Cu is 0.34 V and E° for Cu²⁺/Cu+ is 0.15 V)
(a) 0.49 V
(b) –0.19 V
(c) 0.38 V
(d) –0.38 V

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Question 28. On the basis of the information available from the reaction, 4/3Al + O₂ → 2/3Al₂O₃, ΔG = –827 kJ mol^–1 of O₂, the minimum e.m.f. required to carry out an electrolysis of Al2O3 is (F = 96500 C mol^–1)
(a) 2.14 V
(b) 4.28 V
(c) 6.42 V
(d) 8.56 V 

Question 29. 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% 

Question 30. E° for the cell, Zn | Zn²⁺_(aq) ||Cu²⁺_(aq) | Cu is 1.10 V at 25°C, the equilibrium constant for the reaction
Zn + Cu²⁺ _(aq) → Cu + Zn2+
(aq) is of the order
(a) 10⁺¹⁸ 
(b) 10⁺¹⁷
(c) 10^–28 
(d) 10⁺³⁷

Question 31. The molar conductivity of a 0.5 mol/dm³ solution of AgNO₃ with electrolytic conductivity of 5.76 × 10^–3 S cm^–1 at 298 K is
(a) 2.88 S cm²/mol
(b) 11.52 S cm²/mol
(c) 0.086 S cm²/mol
(d) 28.8 S cm²/mol

Question 32. 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

Question 33. 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

Question 34. 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)

Question 35. 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
(e) silver electrode acts as anode and E°_cell is + 1.14 V

Question 36. The metal used to recover copper from a solution of CuSO₄ is 
(a) Fe
(b) He
(c) Na
(d) Ag

Question 37. The standard electrode potential is measured by 
(a) electrometer
(b) voltmeter
(c) pyrometer
(d) galvanometer

Question 38. 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

Question 39. 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

Question 40. 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)

Question 41. For a cell given below,
Ag l Ag⁺ ll Cu²⁺ l Cu
Ag⁺ +e^– → Ag,E° = x
Cu ²⁺ + 2e^– → Cu, E° = y E°_cell is
(a) x + 2y
(b) 2x + y
(c) y – x
(d) y – 2x   

Question 42. A standard hydrogen electrode has zero electrode potential because 
(a) hydrogen is easier to oxidise
(b) this electrode potential is assumed to be zero
(c) hydrogen atom has only one electron
(d) hydrogen is the lightest element   

Question 43. For the following cell with hydrogen electrodes at two different pressures p₁ and p₂
Pt(H₂ ) l H⁺ (aq) l Pt (H₂ ) emf is given by
Pt 1M P₂ 
(a) RT/F log_e P₁/P₂
(b) RT/2F log_e P₁/P₂
(c) RT/F log_e P₂/P₁
(d) RT/2F log_e P₂/P₁ 

Question 44. 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   

Question 45. For hydrogen-oxygen fuel cell at 1 atm and 298 K
H₂ (g) + 1/2 O₂ (g) → H₂O(l), ΔG = – 240 kJ
E° for the cell is approximately (Given, F = 96500 C)
(a) 2.48 V
(b) 1.25 V 
(c) 2.5 V
(d) 1.24 V   

Question 46. The rusting of iron takes place as follows
2H⁺ + 2e^– + 1/2 O₂ →H₂O(/);E° = + 1.23 V
Fe²⁺ + 2e^– → Fe (s);E° = – 0.44 V
Calculate ΔG° for the net process. 
(a) – 322 kJ mol^-1
(b) – 161 kJ mol^-1
(c) – 152 kJ mol^-1
(d) – 76 kJ mol^-1   

Question 47. 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

Question 48. 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.

Question 49. 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  

Question 50. 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 

Question 51. 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.

Question 52. 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. 

Question 53. 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

Question 54. 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. 

Question 55. 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

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