The standard electrode potentials of Zn and Ni respectively are -

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91.

The standard electrode potentials of Zn and Ni respectively are - 0.76 V and - 0.25 V. Then the standard emf of the spontaneous cell by coupling these under standard conditions is

  • +1.01 V

  • -0.51 V

  • +0.51 V

  • +0.25 V


C.

+0.51 V

The standard electrode potential of Zn(E°anode) = -0.76 V

The standard electrode potential of Ni(E°anode) = -0.25 V

From equation,

cell = E°(cathode) - E°(anode)

        = -0.25 -(-0.76)

        = +0.51 V


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92.

How many moles of platinum will be deposited on the cathode when 0.60 F of electricity is passed through a 1.0 M solution of Pt4+?

  • 0.60 mol

  • 0.15 mol

  • 0.30 mol

  • 0.45 mol


93.

A 250 W electric bulb of 80% efficiency emits a light of 6626 Å wavelength. The number of photons emitted per second by the lamp is (h = 6.636 x 10-34 Js)

  • 1.42 × 1017 

  • 2.18 × 1016 

  • 6.66 × 1020 

  • 2.83 × 1016 


94.

Consider the following elecrolytic cells

(i) M (s) | M2+ (aq), 0.1 M || X2+ (aq), 0.01 M | X (s)

(ii) M (s) | M2+ (aq), 0.1 M || X2 (aq), 0.01 M | X (s)

(iii) M (s) | M2+ (aq), 0.1 M || X2 (aq), 0.01 M | X (s)

The cell EMF of the above cells are E1, E2 and E3 respectively. Which one of the following is true?

  • E3 > E2 > E1

  • E1 > E2 > E3

  • E2 > E3 > E1

  • E1 > E3 > E2


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95.

When the total cell emf of a volatic cell is greater than zero, which of the following is true about the reaction quotient Q and free energy change G for the cell reaction?

  • Q is less than one and G is greater than zero

  • Q is greater than one and G is greater than zero

  • Q is greater than one and G is less than zero

  • Q is zero and G is greater than zero


96.

In dry cell, what acts as a negative electrode?

  • Zinc

  • Graphite

  • Ammonium chloride

  • Manganese dioxide


97.

A weak electrolyte having the limiting equivalent conductance of 400 S cm2 g equiv-1 at 298 K is 2% ionized in its 0.1 N solution. The resistance of this solution (in ohm) in an electrolytic cell of cell constant 0.4 cm-1 at this temperature is

  • 200

  • 300

  • 400

  • 500


98.

Given that the standard reduction potentials for M/ M and N+ / N electrodes at 298 K are 0.52 V and 0.25 V respectively. Which of the following is correct in respect of the following electrochemical cell?

M | M+ || N+ | N

  • The overall cell reaction is a spontaneous reaction

  • The standard EMF of the cell is -0.27 V

  • The standard EMF of the cell is 0.77 V

  • The standard EMF of the cell is -0.77 V


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99.

The standard redox potential for the reactions, Mn2+ + 2e- → Mn and Mn3+ + e- → Mn2+ are -1.18 V and 1.51 V respectively. What is the redox potential for the reaction Mn3+ + 3e- → Mn?

  • 0.33 V

  • 1.69 V

  • - 0.28 V

  • -0.85 V


100.

The limiting molar conductivities of HCl, CH3COONa and NaCl are respectively 425, 90 and 125 mho cm2 mol-1 at 25°C. The molar conductivity of 0.1 M CH3COOH solution is 7.8 mho cm2 mol-1 at the same temperature. The degree of dissociation of 0.1 M acetic acid solution at the same temperature is

  • 0.10

  • 0.02

  • 0.15

  • 0.03


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