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

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

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 

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

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

In dry cell, what acts as a negative electrode?

• Zinc

• Graphite

• Ammonium chloride

• Manganese dioxide

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

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

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

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