Electrochemistry PYQs Set 9 (PDF)

Set 9 of 13 · Questions 241-270 of 363

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Electrochemistry · Set 9 (Q241-270)
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241. $A 5-ampere current is passed through a solution of zinc sulphate for 40 minutes. The amount of zinc deposited at the cathode is$ (1) $0.4065 g$ (2) $65.04 g$ (3) $40.65 g$ (4) $4.065 g$ 242. $The standard e.m.f of a galvanic cell involving cell reaction with n = 2 is found to be 0.295 V at 2 5^{o} C. The equilibrium constant of the reaction would be () Given (F = 96500 Cmol^{- 1}, R = 8.314 JK^{- 1} mol^{- 1})$ (1) $2.0 \times 1 0^{11}$ (2) $4.0 \times 1 0^{12}$ (3) $1.0 \times 1 0^{2}$ (4) $1.0 \times 10^{10}$ 243. $The Gibb’s energy for the decomposition of A l_{2} O_{3} at 500 C is as follows \frac{2}{3} A l_{2} O_{3} \to \frac{4}{3} A l + O_{2}, ∆_{r} G = + 960 k J m o l^{- 1} The potential difference needed for the electrolytic reduction of aluminium oxide at 50 0^{o} C is at least$ (1) $4.5 V$ (2) $3.0 V$ (3) $2.5 V$ (4) $5.0 V$ 244. $The E_{M^{3 +} / M^{2 +}}^{0} values for Cr, Mn, Fe and Co are - 0.41, + 1.57, + 0.77 and + 1.97 V respectively. For which one of these metals, the change in oxidation state from +2 to +3 is easiest$ (1) $Cr$ (2) $Mn$ (3) $Fe$ (4) $Co$ 245. $The variation of molar conductivity with concentration of an electrolyte (X) in aqueous solution is shown in figure. The electrolyte X is$ (1) $NaCl$ (2) $HCl$ (3) $CH_{3} COOH$ (4) $KNO_{3}$ 246. $The E^{\circ} of Ce^{4 +} / Ce^{3 +} = 1.6 V Fe^{3 +} / Fe^{2 +} = 0.76 V the E^{\circ} of Fe^{3 +} oxidising Ce^{3 +} is$ (1) $+ 0.84 V$ (2) $- 0.84 V$ (3) $- 2.32 V$ (4) $+ 1.5 V$ 247. $The molar conductivity of a 0.5 m o l / d m^{3} solution of A g N O_{3} with electrolytic conductivity of 5.76 \times 1 0^{- 3} S c m^{- 1} at298 K is$ (1) $2.88 S c m^{2} / m o l$ (2) $11.52 S c m^{2} / m o l$ (3) $0.086 S c m^{2} / m o l$ (4) $28.8 S c m^{2} / m o l$ 248. $In a cell that utilizes the reaction Z n_{(s)} + 2H_{(a q)}^{+} \to Zn_{(a q)}^{2 +} + H_{2 (g)}, addition of H_{2} S O_{4} to cathode compartment will :$ (1) $lower the E and shift equilibrium to the left.$ (2) $lower the E and shift the equilibrium to the right.$ (3) $increase the E and shift the equilibrium to the right.$ (4) $increase the E and shift the equilibrium to the left.$ 249. $The reaction occurs in which of the given galvanic cell? \frac{1}{2} H_{2} (g) + AgCl (s) ⇌ H^{+} (aq) + C l^{-} (aq) + Ag (s)$ (1) $Pt\| H_{2} (g)\|HCl(so l^{n})\|AgCl(s)\|Ag$ (2) $Ag\| AgCl(s)\|KCl(so l^{n})\| A g N O_{3} \|Ag$ (3) $Pt\| H_{2} (g)\|HCl(so l^{n})\| A g N O_{3} (so l^{n})\|Ag$ (4) $Pt\| H_{2} (g)\|KCl(so l^{n})\|AgCl(s)\|Ag$ 250. $For the reduction of silver ions with copper metal, the standard cell potential was found to b e + O .46 V at 2 5^{o} C . The value of standard Gibbs energy, ∆ G^{o} will be$ (1) $- 89.0 k J$ (2) $- 89.0 J$ (3) $- 44.5 k J$ (4) $- 98.0 k J$ 251. $How long (approximate) should water be electrolysed by passing through 100 amperes current so that the oxygen released can completely burn 27.66 g of diborane?$ (1) $3.2 hours$ (2) $1.6 hours$ (3) $6.4 hours$ (4) $0.8 hours$ 252. $Match List - I with List - II List-I (Parameter) (A) Cell constant (B) Molar conductivity (C) Conductivity (D) Degree of dissociation List-II (Unit) (I) S cm^{2} mol^{- 1} (II) Dimensionless (III) m^{- 1} (IV) Ω^{- 1} m^{- 1} of electrolyte Choose the most appropriate answer from the options given below :$ (1) $(A)-(III), (B)-(I), (C)-(IV), (D)-(II)$ (2) $(A)-(III), (B)-(I), (C)-(II), (D)-(IV)$ (3) $(A)-(I), (B)-(IV), (C)-(III), (D)-(II)$ (4) $(A)-(II), (B)-(I), (C)-(III), (D)-(IV)$ 253. $The emf of cell TI \| TI (0.001 M) \| (Cu^{2 +} (0.01 M)) Cu is 0.83 V at 298 K . It could be increased by :$ (1) $decreasing concentration of both Tl^{+} and Cu^{2 +} ions$ (2) $increasing concentration of Cu^{2 +} ions$ (3) $increasing concentration of T I^{+} ions$ (4) $increasing concentration of both TI+and Cu^{2 +} ions$ 254. $Given below are two statements : Statement I: The limiting molar conductivity of KCl (strong electrolyte) is higher compared to that o f C H_{3} COOH (weak electrolyte). Statement II: Molar conductivity decreases with decrease in concentration of electrolyte. In the light of the above statements, choose the answer from the options given below :$ (1) $Statement I is true but Statement II is false.$ (2) $Statement I is false but Statement II is true.$ (3) $Both Statement I and Statement II are true.$ (4) $Both Statement I and Statement II are false.$ 255. $Given:(i) C u^{2 +} + 2 e^{-} \to C u, E^{o} = 0.337 V (ii) C u^{2 +} + e^{-} \to C u^{+}, E^{o} = 0.153 V Electrode potential, E^{o} for the reaction, C u^{+} + e^{-} \to C u, will be$ (1) $0.90 V$ (2) $0.30 V$ (3) $0.38 V$ (4) $0.52 V$ 256. $Given below are half cell reactions: MnO_{4}^{-} + 8 H^{+} + 5 e^{-} \to Mn^{2 +} + 4 H_{2} O E_{Mn^{2 +} / MnO_{4}^{-}}^{o} = - 1.510 V \frac{1}{2} O_{2} + 2 H^{+} + 2 e^{-} \to H_{2} O E_{O_{2} / H_{2} O} = + 1.223 V Will the permanganate ion, MnO_{4}^{-} liberate O_{2} from water in the presence of an acid?$ (1) $No because E_{cell}^{0} = - 2.733 V$ (2) $Yes, because E_{cell}^{0} = + 0.287 V$ (3) $No, because E_{cell}^{0} = - 0.287 V$ (4) $Yes, because E_{cell}^{0} = + 2.733 V$ 257. $The standard electrode potential E^{Q} and its temperature coefficient for a cell are 2 V and -5 \times 1 0^{- 4} VK-1 at 300 K respectively. The cell reaction is Zn(s) + Cu^{2 +} (aq) ® Zn^{2 +} (aq) + Cu(s) The standard reaction enthalpy (D_{r} H^{Q}) at 300 K in kJ mol-1 is: (Use R = 8 J K^{-1} mol-1 and F = 96,000 Cmol^{-1})$ (1) $206.4$ (2) $-384.0$ (3) $192.0$ (4) $-412.8$ 258. $Under which of the following conditions E value of the cell, for the cell reaction given is maximum? Zn (s) + Cu^{2 +} (aq, c_{1}) ⟶ Cu (s) + Zn^{2 +} (aq, c_{2}) (\frac{2.303 R T}{F} at 298 K = 0.059 V, E_{Zn^{2 +} / Zn}^{\circ} = - 0.76 V, E_{Cu^{2 +} / Cu}^{\circ} = + 0.34 V)$ (1) $C_{1} = 0.1 M, C_{2} = 0.01 M$ (2) $C_{1} = 0.01 M, C_{2} = 0.1 M$ (3) $C_{1} = 0.1 M, C_{2} = 0.2 M$ (4) $C_{1} = 0.2 M, C_{2} = 0.1 M$ 259. $Resistance of a conductivity cell (cell constant 129 m^{- 1}) filled with 74.5 ppm solution of KC1 is 100 Ω (labelled as solution 1). When the same cell is filled with KC1 solution of 149 ppm, the resistance is 50 Ω (labelled as solution 2). The ratio of molar conductivity of solution 1 and solution 2 is i.e. \frac{\land _{1}}{\land _{2}} = x \times 1 0^{- 3} . The value of x is_____.(Nearest integer)Given, molar mass of KC1 is 74.5 g m o l^{- 1}$ 260. $The solubility product of a sparingly soluble salt A_{2} X_{3} is 1.1 x 1 0^{- 23} . If specific conductance of the solution is 3 x 1 0^{- 5} S m^{- 1}, the limiting molar conductivity of the solution is x \times 1 0^{- 3} S m^{2} m o l^{- l} . The value of x is__________.$ 261. $A dilute solution of sulphuric acid is electrolysed using a current of 0.10 A for 2 hours to produce hydrogen and oxygen gas. The total volume of gases produced at STP is________c m^{3} . (Nearest integer) [Given : Faraday constant F = 96500 C mol"^{1} at STP, molar volume of an ideal gas is 22. 7 L m o l^{- 1}]$ 262. $The equilibrium constant for the reaction Zn(s) + S n^{2 +} (aq) ⇌ Z n^{2 +} (aq) + Sn(s) is 1 x 1 0^{20} at 298 K. The magnitude of standard electrode potential of Sn/ S n^{2 +} if E_{Z n^{+} / Z n}^{0} = -0.76 V is _______x 1 0^{- 2} V. (Nearest integer) Given: \frac{2.303 R T}{F} = 0.059V$ 263. $If the conductivity of mercury at 0^{0} C is 1.07 \times 1 0^{6} S m^{- 1} and the resistance of a cell containing mercury is 0.243 Ω, then the cell constant of the cell is x \times 1 0^{4} m^{- 1} . The value of x is ____.(Nearest integer)$ 264. $The cell potential for the following cell Pt H_{2} (g) \|\| H^{+} (aq) \|\| C u^{2 +} (0.01M) \| Cu(s) is 0.576 V at 298 K. The pH of the solution is ___ .(Nearest integer)$ 265. $Consider the cell P t_{(s)} H_{2} (g,1 atm) H^{+} (aq, l M)\| F e^{3 +} (aq), F e^{2 +} (aq)\|Pt(s) When the potential of the cell is 0.712 V at 298 K, the ratio [F e^{2 +}]/[F e^{3 +}] is_________. (Nearest integer) Given: F e^{3 +} + e^{-} = F e^{2 +}, E° F e^{3 +}, F e^{2 +} \|Pt = 0.771 \frac{2.303 R T}{F} = 0.06 V$ 266. $The specific conductance of 0.0025M acetic acid is 5 x 1 0^{- 5} S c m^{- 1} at a certain temperature. The dissociation constant of acetic acid is___________x 1 0^{- 7} . (Nearest integer) Consider limiting molar conductivity of C H_{3} COOH as 400 S c m^{2} m o l^{- 1}$ 267. $The conductivity of a weak acid HA of concentration 0.001 m o l L^{- 1} is 2.0 \times 1 0^{- 5} S c m^{- 1} . If Λ_{m}^{0} (H A) = 190 S c m^{2} m o l^{- 1}, the ionization constant (_{a}^{K}) of HA is equal to \times 1 0^{- 6} (Round off to the Nearest Integer)$ 268. $Two students use the same stock solution of Z n S O_{4} and different solutions of C u S O_{4} to make Daniel cell. The emf of one cell is 0.03 V higher than the other. The concentration of C u S O_{4} solution in the cell with higher emf value is 0.5 M. Find out the concentration of C u S O_{4} solution in the other cell. . (Given : \frac{2.303 R T}{F} = 0.06)$ 269. $For a cell, Cu(s) \|Cu2+(0.001M\| \| Ag^{+} (0.01M)\| Ag(s) the cell potential is found to be 0.43 V at 298 K. The magnitude of standard electrode potential for Cu2+/Cu is___x10-2V. (Given : E_{A g^{+} / Ag}^{⊙} = 0.80 Vand \frac{2.303 RT}{F} = 0.06 V)$ 270. $A metal surface of 100 c m^{2} area has to be coated with nickel layer of thickness 0.001 mm. A current of 2A was passed through a solution of Ni (N O_{3})_{2} for 'x' seconds to coat the desired layer. The value of x is_________. (Nearest integer) (ρ Ni (density of Nickel) is 10 g m L^{- 1}, Molar mass of Nickel is 60 g m o l^{- 1} F = 96500 C m o l^{- 1})$