Tiêu đề UNIT 2 ELECTROCHEMISTRY-1.pdf ✅

Page| 1 3.ELECTROCHEMISTRY Single Correct Answer Type 1. The desired amount of charge for obtaining one mole of Al from Al3+ is a) 96500 C b) 2 × 96500 C c) 3 × 96500 C d) 96500 2 C 2. A certain current liberates 0.504 g of hydrogen in 2 hr. How many gram of copper can be liberated by the same current flowing for the same time in CuSO4solution? a) 12.7 b) 16 c) 31.8 d) 63.5 3. If the Ecell ° for a given reaction has a negative value, then which of the following gives the correct relationships for the value of ∆G°and Keq? a) ∆G° > 0; Keq < 1 b) ∆G° > 0; Keq > 1 c) ∆G° < 0; Keq > 1 d) ∆G° < 0; Keq < 1 4. The Edison storage cell is represented as : Fe(s) + FeO(s)| KOH(aq)| Ni2O3 (s)|Ni2O3 (s)| Ni(s) The half reactions are Ni2O3 (s) + H2O(l) + 2e − → 2NiO(s) + 2OH−; E° = +0.40 V FeO(s) + H2O(l) + 2e − → Fe(s) + 2OH−; E° = −0.87 V Choose the incorrect statement a) Eanode increases with increase in concentration of OH− b) Ecathode decreases with increase in concentration of OH− c) Ecell ° = 1.27 V d) Ecell increases with increase in concentration of FeO 5. 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 6. The standard reduction potential for Fe2+|Fe and Sn2+|Sn electrodes are −0.44 V and −0.14 V respectively. For the cell reaction, Fe 2+ + Sn ⟶ Fe + Sn 2+, the standard e.m.f. is: a) + 0.30 V b) 0.58 V c) + 0.58 V d) − 0.30 V 7. Electrolytes when dissolved in water dissociates into ions because a) They are unstable b) The water dissolves it c) The force of repulsion increases
Page| 2 d) The force of electrostatic attraction are broken down by water 8. Which ion has exceptionally higher Λ ∞ values? a) H + b) K + c) NH2 − d) OH 9. Limiting molar ionic conductivities of a uni-univalent electrolyte are 57 and 73. The limiting molar conductivity of the solution will be : a) 130 Scm2mol−1 b) 65 Scm2mol−1 c) 260 Scm2mol−1 d) 187 Scm2mol−1 10. Molten NaCl conducts electricity due to the presence of : a) Free electrons b) Free molecules c) Free ions d) Atoms of Na and Cl 11. The emf of the cell, (EZn2+ /Zn = −0.76 V) Zn / Zn2+ (1 M) || Cu2+ (1 M) | Cu (ECu2+ /Cu = +0.34 V) will be a) +1.10 V b) -1.10 V c) +0.42 V d) -0.42 V 12. Which represents a concentration cell? a) PtH2|HCl|| HCl |PtH2 c1 c2 b) PtH2|HCl||Cl2|Pt c1 c) Zn|Zn2+||Cu2+|Cu d) Fe|Fe 2+||Cu 2+|Cu 13. In electrolysis of aqueous copper sulphate, the gas at anode and cathode are a) O2and H2 b) H2 and O2 c) SO2 and H2 d) SO3 and O2 14. Consider the reaction, Mn+(aq) + ne ⟶ M0 (s). The standard reduction potential values of the metals M1, M2 and M3 are −0.34 V, −3.05 V and −1.66 V respectively. The order of their reducing power will be : a) M1 > M2 > M3 b) M3 > M2 > M1 c) M1 > M3 > M2 d) M2 > M3 > M1 15. The charge required to liberate one gram equivalent of an element is a) 96500 F b) 1 F c) 1 C d) None of these 16. What will be pH of aqueous solution of electrolyte in electrolytic cell during electrolysis of CuSO4(aq) between graphite electrodes? a) pH = 14.0 b) pH > 7.0 c) pH < 7.0 d) pH = 7.0 17. In an electrolytic cell, the anode and cathode are respectively represented as : a) Positive electrode, negative electrode b) Negative electrode, positive electrode c) Both positive and negative electrode d) None of the above 18. The cell reaction is spontaneous, when a) Ered ° is negative b) Ered ° is positive c) ΔG ° is negative d) ΔG ° is positive
Page| 3 19. The emf of the cellMg| Mg2+(0.01 M)|| Sn2+(0.1 M)|Sn at 298 K is (Given, EMg2+,Mg ° = −2.34 V, −2.34 V, ESn2+,Sn ° = −0.14 V) a) 2.23 V b) 1.86 V c) 1.56 V d) 3.26 V 20. When an aqueous solution of lithium chloride is electrolysed using graphite electrodes : a) pH of the resulting solution increases b) pH of the resulting solution decreases c) As the current flows, pH of the solution around the cathode increases d) None of the above 21. In electrolytic purification, which of the following is made of impure metal? a) Anode b) Cathode c) Both (a) and (b) d) None of these 22. The specific conductivity of 0.1 N KCl solution is 0.0129 Ω −1 cm−1 . The resistance of the solution in the cell 100Ω. The cell constant of the cell will be a) 1.10 b) 1.29 c) 0.56 d) 2.80 23. Which graph correctly correlates ECell as a function of concentrations for the cell (for different values of M and Mʹ)? Zn(s) + Cu 2+(M) ⟶ Zn2+(Mʹ) + Cu(s); E°Cell = 1.10 V X − axis ∶ [Zn 2+] [Cu 2+] , Y − axis ∶ ECell a) b) c) d) 24. In acidic medium MnO4 − is converted to Mn2+. The quantity of electricity in faraday required to reduce 0.5 mole of MnO4 − to Mn2+ would be a) 2.5 b) 5 c) 1 d) 0.5 25. In electrolysis, oxidation takes place at: a) Anode b) Cathode c) The anode as well as cathode d) The surface of electrolyte solution 26. A depolariser used in dry cell batteries is : a) Ammonium chloride b) Manganese dioxide c) Potassium hydroxide d) Sodium phosphate 27. The E°M3+/M2+ values for Cr, Mn, Fe and Co are −0.41, +1.57, +0.77and+1.97 V respectively. For which one of these metals, the change in oxidation state from +2 to +3 is easiest?
Page| 4 a) Fe b) Mn c) Co d) Cr 28. The standard reduction electrode potential values of the elements A, B and C are + 0.68, ⎯2.50 and ⎯ 0.50 V respectively. The order of their reducing power is : a) A > B > C b) A > C > B c) C > B > A d) B > C > A 29. The number of electrons involved in the reaction when a faraday of electricity is passed through an electrolyte in solution is : a) 12 × 1046 b) 96500 c) 8 × 1016 d) 6.02 × 1023 30. The electrolysis of a solution resulted in the formation of H2at the cathode and Cl2 at the anode. The liquid is: a) Pure water b) H2SO4 solution c) NaCl solution in water d) CuCl2 solution in water 31. The passage of electricity in the Daniell cell when Zn and Cu electrodes are connected: a) From Cu to Zn inside the cell b) From Cu to Zn outside the cell c) From Zn to Cu outside the cell d) None of the above 32. Ni / Ni2+ [1.0 M] || Au3+ [1.0 M] / Au where E ° for Ni2+ /Ni is − 0.250 V; and E ° for Au3+ / Auis 0.150 V. The emf of the cell is a) +1.25 V b) -1.75 V c) +1.75 V d) +0.4 V 33. The product obtained at anode when 50% H2SO4 aqueous solution is electrolysed using platinum electrodes is a) H2SO3 b) H2S2O8 c) O2 d) H2 34. The approximate e.m.f. of a dry cell is : a) 2.0 V b) 1.2 V c) 6 V d) 1.5 V 35. E1,E2, and E3 are the emfs of the following three galvanic cells respectively I. Zn (s) | Zn2+ (0.1 M) || Cu2+ (1 M) | Cu (s) II. Zn (s) | Zn2+ (1 M) || Cu2+ (1 M) | Cu (s) III. Zn (s) | Zn2+ (1 M) || Cu2+ (0.1 M) | Cu (s) Which one of the following is true? a) E2 > E1 > E3 b) E1 > E2 > E3 c) E3 > E1 > E2 d) E3 > E2 > E1 36. The fraction of the total current carried by an ion is known as: a) Transport number of that ion b) Conductance of that ion