Electrochemistry PYQs Set 5 (PDF)

Set 5 of 13 · Questions 121-150 of 363

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Electrochemistry · Set 5 (Q121-150)
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121. $If hydrogen electrodes dipped in two solutions of pH = 3 and pH = 6 are connected by a salt bridge, the emf of the resulting cell is$ (1) $0.177 V$ (2) $0.3 V$ (3) $0.052 V$ (4) $0.104 V$ 122. $Which of the following cannot be considered as application of electrochemical series?$ (1) $Relative strength of reducing agent$ (2) $Use of SHE in automobile battery$ (3) $Relative strength of oxidising agent$ (4) $Spontaneity of redox reaction$ 123. $Resistance of 0.2 M solution of an electrolyte is 50 Ω. The specific conductance of the solution is 1.4 S m^{-1} . The resistance of 0.5 M solution of the same electrolyte is 280 Ω. The molar conductivity of 0.5 M solution of the electrolyte in S m^{2} m o l^{-1} is :$ (1) $5 \times 1 0^{- 4}$ (2) $5 \times 1 0^{- 3}$ (3) $5 \times 103$ (4) $5 \times 102$ 124. $For spontaneity of a cell, which is correct?$ (1) $Δ G = + ve, Δ E = + ve$ (2) $Δ G = - ve$ (3) $Δ G = 0, Δ E = 0$ (4) $Δ G = - ve, Δ E = 0$ 125. $The reaction at cathode in the cells commonly used in clocks involves.$ (1) $reduction of Mn from +7 to +2$ (2) $reduction of Mn from +4 to +3$ (3) $oxidation of Mn from +3 to +4$ (4) $oxidation of Mn from +2 to +7$ 126. $Consider the following relations for emf of an electrochemical cell(i) EMF of cell = (Oxidation potential of anode) ‐(Reduction potential of cathode)(ii) EMF of cell = (Oxidation potential of anode) + ( Reduction potential of cathode)(iii) EMF of cell = (Reductional potential of anode) + (Reduction potential of cathode) (iv) EMF of cell = (Oxidation potential of anode) ‐(Oxidation potential of cathode)Which of the above relations are correct?$ (1) $(iii) and (i)$ (2) $(i) and (ii)$ (3) $(iii) and (iv)$ (4) $(ii) and (iv)$ 127. $Salts of A (atomic weight 8 ), B (atomic weight 18 ) and C (atomic weight 50 ) were electrolysed under identical conditions using the same quantity of electricity. It was found that 2.4 g of A was deposited, the weight of B and C deposited are 1.8 g and 7.5 g, respectively. The valences of A, B and C are, respectively,$ (1) $3,1 and 2$ (2) $1,2 and 3$ (3) $1,3 and 2$ (4) $3,2 and 1$ 128. $The molar conductivities Λ_{NaOAc}^{0} and Λ_{HCl}^{0} at infinite dilution in water at 25°C are 91.0 and 426.2 Scm^{2} /mol respectively. To calculate Λ_{HOAc}^{0}, the additional value required is :$ (1) $Λ_{H_{2} O}^{0}$ (2) $Λ_{KCl}^{0}$ (3) $Λ_{NaOH}^{0}$ (4) $Λ_{NaCl}^{0}$ 129. $Identify the gas produced due to reduction of NH_{4}^{+} ions at cathode during working of dry cell.$ (1) $Ammonia$ (2) $Hydrogen$ (3) $Hydrogen chloride$ (4) $Chlorine$ 130. $The resistance of 0.1 M weak acid HA in a conductivitycellis 2 \times 10^{3} ohm . Thecellconstant of the cell is 0.78 C m^{- 1} and λ^{6}_{m} of acid H A is 390 S cm^{2} mol^{- 1} . The pH of the solution is$ (1) $3.3$ (2) $4.2$ (3) $5$ (4) $3$ 131. $A solution of Ni (NO_{3})_{2} is electrolysed between platinum electrodes using 0.1 Faraday electricity. How many mode of Ni will be deposited at the cathode?$ (1) $0.05$ (2) $0.20$ (3) $0.15$ (4) $0.10$ 132. $Which of the following does not conduct electricity?$ (1) $Fused NaCl$ (2) $Solid NaCl$ (3) $Brine solution$ (4) $Copper$ 133. $How can an electrochemical cell be converted into an electrolytic cell?$ (1) $Applying an external opposite potential lower than E^{0} cell.$ (2) $Reversing the flow of ions in salt bridge.$ (3) $Applying an external opposite potential greater than E^{0} cell-$ (4) $Exchanging the electrodes at anode and cathode.$ 134. $The amount of current in faraday, required for the reduction of 1 mol of Cr_{2} O_{7}^{2 -} ions to Cr^{3 +} is$ (1) $1 F$ (2) $2 F$ (3) $6 F$ (4) $4 F$ 135. $For a cell given below: Ag (Ag^{+}) (Cu^{2 +}) Cu Ag^{+} - + e^{-} \to A + g E^{\circ} = x C u^{2 +} + 2 e^{-} \to, E^{\circ} = y E^{\circ} cell is:$ (1) $x + 2y$ (2) $2x + y$ (3) $y -x$ (4) $y - 2x$ 136. $The molar conductivity of 0.027 M methanoic acid is 40.42 Scm^{2} mol^{- 1} . The value of dissociation constant of this acid is (Given λ_{H^{+}}^{\circ} = 349.6 S cm^{2} mol^{- 1} and λ_{HCOO^{-}}^{\circ} = 54.6 S (cm^{2} mol^{- 1})$ (1) $1.5 \times 10^{- 5}$ (2) $6.0 \times 10^{- 5}$ (3) $4.5 \times 10^{- 4}$ (4) $3.0 \times 10^{- 4}$ 137. $For a cell involving two electron changes, E_{cell} = 0.3 V at 25^{\circ} C . The equilibrium constant of the reaction is$ (1) $10^{- 10}$ (2) $3 \times 10^{- 2}$ (3) $10$ (4) $10^{10}$ 138. $The one which decreases with dilution is$ (1) $conductance$ (2) $specific conductance$ (3) $equivalent conductance$ (4) $molar conductance.$ 139. $Consider the following electrode processes of a cell, C l^{-} \to \frac{1}{2} C l_{2} + e^{-}, MCl + e^{-} \to M + C l^{-} If EMF of this cell is - 1.140 V and E^{\circ} value of the cell is - 0.55 V at 298 K, the value of the equilibrium constant of the sparingly soluble salt MCl is in the order of$ (1) $10^{- 10}$ (2) $10^{- 8}$ (3) $10^{- 7}$ (4) $10^{- 11}$ 140. $For Cr_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 Cr^{3 +} + 7 H_{2} O, E^{\circ} = 1.33 V At (Cr_{2} O_{7}^{2 -}) = 4.5 millimole, (Cr^{3 +}) = 15 millimole, E is 1.067 V . The pH of the solution is nearly equal to$ (1) $2$ (2) $3$ (3) $5$ (4) $4$ 141. $In the electrolysis of aqueous sodium chloride solution, which of the half cell reaction will occur at anode?$ (1) $Cl_{(aq)}^{-} \to \frac{1}{2} Cl_{2} + e^{- m}; E_{cell}^{\circ} = 1.36 volts$ (2) $2 H_{2} O_{(n)} \to O_{2} + 4 H^{+} + 4 e^{-}; E_{cell}^{o} = 1.23 volts$ (3) $Na_{(aq)}^{+} + e^{-} ⟶ Na_{(s)}; E^{\circ} = - 2.71 volts$ (4) $H_{(aq)}^{+} + e ⟶ \frac{1}{2} H_{2}; E_{cell}^{\circ} = 0.00 volts$ 142. $The electric charge for electrode deposition of one equivalent of a substance is equal to$ (1) $1 A / s$ (2) $193000 coulombs$ (3) $\frac{96500}{( Atomic weight of the substance )}$ (4) $Charge on 1 mole of electrons$ 143. $Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R: Assertion A: In equation Δ_{r} G = - nF E_{cell}, value of Δ_{r} G depends on n . Reasons R: E_{cell} is an intensive property and Δ_{r} G is an extensive property. choose the correct answer from the options given below:$ (1) $A is false but R is true.$ (2) $Both A and R are true and R is the correct explanation of A .$ (3) $Both A and R are true but R is NOT the correct explanation of A .$ (4) $A is true but R is false$ 144. $If the E_{cell}^{\circ} of an equilibrium reaction A (s) + 2 B^{2 +} (aq) ⟶ A^{2 +} (aq) + 2 B (s) at 298 K is 0.59 V, the equilibrium constant K_{c} is$ (1) $1.0 \times 10^{10}$ (2) $1.0 \times 10^{2}$ (3) $1.0 \times 10^{- 20}$ (4) $1.0 \times 10^{20}$ 145. $When the same quantity of electricity is passed through the aqueous solutions of the given electrolytes for the same amount of time, which metal will be deposited in maximum amount on the cathode?$ (1) $ZnSO_{4}$ (2) $FeCl_{3}$ (3) $AgNO_{3}$ (4) $NiCl_{2}$ 146. $Which of the following acts as oxidising agent in hydrogen-oxygen fuel cell?$ (1) $H_{2}$ (2) $O_{2}$ (3) $KOH$ (4) $C$ 147. $At 2 5^{0} C molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 o h m^{- 1} c m^{2} m o l^{- 1} and at infinite dilution its molar conductance is 238 o h m^{- 1} c m^{2} m o l^{- 1} . The degree of ionisation of ammonium hydroxide at the same concentration and temperature is$ (1) $4.008%$ (2) $40.800%$ (3) $2.080%$ (4) $20.800%$ 148. $For a cell involving one electron E^{\circ} cell = 0.59 V at 298 K , the equilibrium constant for the cell reaction is (Given that) \frac{2.303 RT}{F} = 0.059 V at (T = 298 K)$ (1) $1.0 \times 10^{2}$ (2) $1.0 \times 10^{5}$ (3) $1.0 \times 10^{10}$ (4) $1.0 \times 10^{30}$ 149. $The molar conductivity of 0.007 M acetic acid is 20 S cm^{2} mol^{- 1} . What is the dissociation constant of acetic acid? Choose the correct option. (Λ_{H^{+}}^{\circ} = 350 S cm^{2} mol^{- 1} Λ_{CH_{3} COO^{-}}^{\circ} = 50 S cm^{2} mol^{- 1})$ (1) $2.50 \times 10^{- 4} mol L^{- 1}$ (2) $1.75 \times 10^{- 5} mol L^{- 1}$ (3) $2.50 \times 10^{- 5} mol L^{- 1}$ (4) $1.75 \times 10^{- 4} mol L^{- 1}$ 150. $The molar conductance of NaCl, HCl and CH_{3} COONa at infinite dilution are 126.45, 426.16 and 91.0 S cm^{2} mol^{- 1} respectively. The molar conductance of CH_{3} COOH at infinite dilution is. Choose the right option for your answer.$ (1) $390.71 S cm^{2} mol^{- 1}$ (2) $698.28 S cm^{2} mol^{- 1}$ (3) $540.48 S cm^{2} mol^{- 1}$ (4) $201.28 S cm^{2} mol^{- 1}$