Electrochemistry PYQs Set 1 (PDF)

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Electrochemistry · Set 1 (Q1-30)
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1. $The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mho c m^{2} and at infinite dilution is 400 mhos c m^{2} . The dissociation constant of this acid is$ (1) $1.25 \times 1 0^{- 6}$ (2) $6.25 \times 1 0^{- 4}$ (3) $1.25 \times 1 0^{- 4}$ (4) $1.25 \times 1 0^{- 5}$ 2. $Which out of the following is a correct equation to show change in molar conductivity with respect to concentration for a weak electrolyte, if the symbols carry their usual meaning :$ (1) $Λ_{m} - Λ_{m}^{0} + A C^{\frac{1}{2}} = 0$ (2) $Λ_{m}^{2} C - K_{a} Λ_{m}^{\circ 2} + K_{a} Λ_{m} Λ_{m} = 0$ (3) $Λ_{m}^{2}_{m} C + K_{a} Λ_{m}^{\circ 2} - K_{a} Λ_{m} Λ_{m}^{\circ} = 0$ (4) $Λ_{m} - Λ_{m}^{\circ} - A C^{\frac{1}{2}} = 0$ 3. $If the resistance of 0.1 MKCl solution in a conductance cell is 300Ω and conductivity is 0.013 Scm^{- 1}, then the value of cell constant is$ (1) $3.9 cm^{- 1}$ (2) $39 m^{- 1}$ (3) $3.9 m^{- 1}$ (4) $0.39 cm^{- 1}$ 4. $The anodic half-cell of lead-acid battery is recharged using electricity of 0.05 Faraday. The amount of PbSO_{4} electrolyzed in g during the process is: (Molar mass of PbSO_{4} = 303 g mol^{- 1})$ (1) $22.8$ (2) $15.2$ (3) $7.6$ (4) $11.4$ 5. $Based on the data given below: E_{Cr_{2} O_{7}^{2 -} / Cr^{3 +}}^{\circ} = 1.33 V E_{Cl_{2} / Cl^{(-)}}^{\circ} = 1.36 V E_{MnO_{4}^{-} / Mn^{2 +}}^{\circ} = 1.51 V E_{Cr^{3 +} / Cr}^{\circ} = - 0.74 V the strongest reducing agent is:$ (1) $Cr$ (2) $Cl^{-}$ (3) $MnO_{4}^{-}$ (4) $Mn^{2 +}$ 6. $In the electrolysis of acidulated water, it is desired to obtain 1.12 cc of hydrogen per second under S.T.P. condition. The current to be passed is$ (1) $9.65 A$ (2) $19.3 A$ (3) $0.965 A$ (4) $1.93 A$ 7. $The standard emf of galvanic cell involving 3 moles of electrons in its redox reaction is 0.59 V . The equilibrium constant for the reaction of the cell is$ (1) $10^{25}$ (2) $10^{20}$ (3) $10^{15}$ (4) $10^{30}$ 8. $Two electrolytic cells are connected in series containing CuSO_{4} solution and molten AlCl_{3} . If in electrolysis 0.4 moles of 'Cu' are deposited on cathode of first cell, the number of moles of 'Al' deposited on cathode of the second cell is$ (1) $0.6 moles$ (2) $0.27 moles$ (3) $0.18 moles$ (4) $0.4 moles.$ 9. $Molar ionic conductivities of divalent cation and anion are 57 S cm^{2} mol^{- 1} and 73 S cm^{2} mol^{- 1} respectively. The molar conductivity of solution of an electrolyte with the above cation and anion will be :$ (1) $187 S cm^{2} mol^{- 1}$ (2) $260 S cm^{2} mol^{- 1}$ (3) $130 S cm^{2} mol^{- 1}$ (4) $65 S cm^{2} mol^{- 1}$ 10. $An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to$ (1) $increase in ionic mobility of ions$ (2) $100% ionisation of electrolyte at normal dilution$ (3) $increase in both i.e., number of ions and ionic mobility of ions$ (4) $increase in number of ions.$ 11. $Consider the following E^{\circ} values E_{F e^{3 +} / F e^{2 +}}^{\circ} = 0.77 V E_{S n^{2 +} / Sn}^{\circ} = - 0.14 V Under standard conditions the potential for the reaction Sn (s) + 2 Fe^{3 +} (aq) ⟶ 2 Fe^{2 +} (aq) + Sn^{2 +} (aq) is$ (1) $1.68 V$ (2) $1.40 V$ (3) $0.91 V$ (4) $0.63 V$ 12. $Which among the following equations represents the reduction reaction taking place in lead accumulator at positive electrode, while it is being used as a source of electrical energy?$ (1) $Pb \to Pb^{2 +}$ (2) $Pb^{4 +} \to Pb$ (3) $Pb^{2 +} \to Pb$ (4) $Pb^{4 +} \to Pb^{2 +}$ 13. $Consider the half‐cell reduction reaction M n^{2 +} + 2 e^{-} \to M n, E^{o} = - 1.18 V M n^{2 +} \to M n^{3 +} + e^{-}, E^{o} = - 1.51 V . The E^{o} for the reaction 3 M n^{2 +} \to M n^{0} + 2 M n^{3 +}, and possibility of the forward reaction are respectively$ (1) $- 4.18 V and yes$ (2) $+ 0.33 V and yes$ (3) $+ 2.69 V and no$ (4) $- 2.69 V and no$ 14. $The molar conductivity is maximum for the solution of concentration$ (1) $0.005 M$ (2) $0.004 M$ (3) $0.001 M$ (4) $0.002 M .$ 15. $In the cell represented by Pb_{(s)} (Pb^{2 +} (1 M)) (Ag^{+} (1 M)) Ag_{(s)}, the reducing agent is$ (1) $Pb$ (2) $Pb^{2 +}$ (3) $Ag$ (4) $Ag^{+}$ 16. $Which among the following metals is employed to provide cathodic protection to iron?$ (1) $Zinc$ (2) $Nickel$ (3) $Tin$ (4) $Lead$ 17. $A metal plate of dimension of (1 \times 2 cm^{2}) has to be coated on both the sides by Cu metal. How long does it take to deposit Cu of 0.01 cm thickness, if 1.5 A current is used? [Electrochemical equivalence of Cu is 0.0003 g / C and the density of Cu is 9 g / cm^{3}]$ (1) $400 s$ (2) $800 s$ (3) $120 s$ (4) $160 s$ 18. $Consider the following reduction processes : Al^{3 +} + 3 e^{-} ⟶ Al (s), E^{0} = - 1.66 V Fe^{3 +} + e^{-} ⟶ Fe^{2 +}, E^{0} = + 0.77 V Co^{3 +} + e^{-} ⟶ Co^{2 +}, E^{0} = + 1.81 V Cr^{3 +} + 3 e^{-} ⟶ Cr (s), E^{\circ} = - 0.74 V The tendency to act as reducing agent decreases in the order :$ (1) $Al > Cr > Fe^{2 +} > Co^{2 +}$ (2) $Cr > Fe^{2 +} > Al > Co^{2 +}$ (3) $Al > Fe^{2 +} > Cr > Co^{2 +}$ (4) $Al > Cr > Co^{2 +} > Fe^{2 +}$ 19. $Calculate molar conductivity of NH_{4} OH at infinite dilution if molar conductivities of Ba (OH)_{2}, BaCl_{2} and NH_{4} Cl at infinite dilution are 520,280, 129 Ω^{- 1} cm^{2} mol^{- 1} respectively.$ (1) $249.0Ω-1 cm2 mol^{- 1}$ (2) $498.0Ω-1 cm2 mol^{- 1}$ (3) $125.0Ω-1 cm2 mol^{- 1}$ (4) $369.0Ω-1 cm2 mol^{- 1}$ 20. $On heating one end of a piece of a metal, the other end becomes hot because of$ (1) $energised electrons moving to the other end$ (2) $minor perturbation in the energy of atoms$ (3) $resistance of the metal$ (4) $mobility of atoms in the metal.$ 21. $If 5 ampers of current is passed for 193 seconds through a solution containing Copper salt, 0.32 g of copper is deposited. What is the oxidation state of the Cu in the salt?$ (1) $+2$ (2) $+1$ (3) $+3$ (4) $+ \frac{3}{2}$ 22. $When a quantity of electricity is passed through CuSO_{4} solution, 0.16 g of copper gets deposited. If the same quantity of electricity is passed through acidulated water, then the volume of H_{2} liberated at STP will be [given : at. wt. of Cu = 64]$ (1) $4.0 cm^{3}$ (2) $56 cm^{3}$ (3) $604 cm^{3}$ (4) $8.0 cm^{3}$ 23. $Limiting molar conductivity of Mg^{2 +} and Cl^{-} ions in water is 106.0 and 76.3 S cm^{2} mol^{- 1} . The limiting molar conductivity of magnesium chloride (in S cm^{2} mol^{- 1}) in water is$ (1) $182.3$ (2) $258.6$ (3) $288.3$ (4) $364.6$ 24. $The metal that cannot be obtained by electrolysis of an aqueous solution of its salts is :$ (1) $Ag$ (2) $Ca$ (3) $Cu$ (4) $Cr$ 25. $Standard electrode potentials are F e^{2 +} / F e; E^{o} = - 0.44 and F e^{3 +} / F e^{2 +}; E^{o} = 0.77 F e^{2 +}, F e^{3 +} and Fe blocks are kept together, then$ (1) $F e^{3 +} increases$ (2) $F e^{3 +} decreases$ (3) $F e^{2 +} / F e^{3 +} remains unchanged$ (4) $F e^{2 +} decreases.$ 26. $Standard reduction potentials of the half reactions are given below: F_{2 (g)} + 2 e^{-} \to 2 F_{(}^{-}_{a q)}; E^{o} = + 2.85 V C l_{2 (g)} + 2 e^{-} \to 2 C l_{(}^{-}_{a q)}; E^{o} = + 1.36 V B r_{2 (l)} + 2 e^{-} \to 2 B r_{(}^{-}_{a q)}; E^{o} = + 1.06 V I_{2 (s)} + 2 e^{-} \to 2 I_{(}^{-}_{a q)}; E^{o} = + O .53 V The strongest oxidising and reducing agents respectively are$ (1) $F_{2} and I^{-}$ (2) $B r_{2} and C l^{-}$ (3) $C l_{2} and B r^{-}$ (4) $C l_{2} and I_{2}$ 27. $For a cell reaction involving a two electron change, the standard emf of the cell is found to be 0.295 V at 25°C. The equilibrium constant of the reaction at 25°C will be:$ (1) $1 \times 1 0^{-10}$ (2) $29.5 \times 1 0^{-2}$ (3) $10$ (4) $1 \times 1 0^{10}$ 28. $If the standard electrode potential for a cell is 2 V at 300 K the equilibrium constant (K) for the reaction Zn (s) + Cu^{2 +} (aq) ⇌ Zn^{2 +} (aq) + Cu (s) at 300 K is approximately (R = 8 JK^{- 1} mol^{- 1}, F = 96000 C mol^{- 1})$ (1) $e^{- 80}$ (2) $e^{- 160}$ (3) $e^{320}$ (4) $e^{160}$ 29. $The standard reduction potentials at 295 K for the following half cells are given below: N O_{3}^{-} + 4 H^{+} + 3e- \to NO(g)+2H2O E° = 0.97 V V^{2 +} (aq)+ 2 e^{-} \to V(s) E° = -1.19 V Fe^{3 +} (aq)+3e- \to Fe(s) E° = -0. 04 V A_{g}^{+} (aq)+e- \to Ag(s) E° = 0.80 V Au^{3 +} (aq)+3e- \to Au(s) E° = 1. 40 V The number of metal(s) which will be oxidised by N O_{3}^{-} in aqueous solution is_____.$ 30. $All the energy released from the reaction X \to Y, Δ_{r} Gº = -193 kJ m o l^{-1} is used for oxidizing M^{+} as M^{+} \to M^{3 +} + 2 e^{-}, Eº = - 0.25 V. Under standard conditions, the number of moles of M^{+} oxidized when one mole of X is converted to Y is : [F = 96500 C m o l^{-1}]$