31.

What type of crystal defect is indicated in the diagram below?

• Frenkel defect

• Frenkel and Schottky defects

• Interstitial defect

• Interstitial defect

In hydrogen-oxygen fuel cell, combustion of hydrogen occurs to

• generate heat

• remove adsorbed oxygen from electrode surfaces

• produce high purity water

• produce high purity water

In first order reaction, the concentration of the reactant decreases from 0.8 M to 0.4 M in 15 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M is

• 30 minutes

• 60 minutes

• 7.5 minutes

• 7.5 minutes

The rate equation for the reaction 2A + B → C is found to be: rate k[A][B]. The correct statement in relation to this reaction is that the

• unit of K must be s^-1

• values of k is independent of the initial concentration of A and B

• rate of formation of C is twice the rate of disappearance of A

• rate of formation of C is twice the rate of disappearance of A

Consider the following E° values


Under standard conditions the potential for the reaction
Sn(s) + 2Fe³⁺(aq) → 2Fe²⁺(aq) + Sn²⁺(aq) is

• 1.68 V

• 0.63 V

• 0.91 V

• 0.91 V

The molar solubility product is K_sp. ‘s’ is given in terms of K_sp by the relation

• 
• 

• s = (256 K_sp)^1/5

• s = (256 K_sp)^1/5

The standard e.m.f of a cell, involving one electron change is found to be 0.591 V at 25°C. The equilibrium constant of the reaction is (F = 96,500 C mol-1: R = 8.314 JK^-1 mol^-1)

• 1.0×10¹

• 1.0×10³⁰

• 1.0×10³⁰

• 1.0×10³⁰

The limiting molar conductivities Λ° for NaCl, KBr and KCl are 126, 152 and 150 S cm² mol^-1 respectively. The Λ° for NaBr is

• 128 S cm² mol^-1

• 302 S cm² mol^-1

• 278 S cm² mol^-1

• 278 S cm² mol^-1

In a cell that utilises the reaction Zn(s) + 2H⁺ (aq) → Zn²⁺(aq) + H₂(g) addition of H₂SO₄ to cathode compartment, will

• lower the E and shift equilibrium to the left

• increases the E and shift equilibrium to the left

• increase the E and shift equilibrium to the right

• increase the E and shift equilibrium to the right

Which one the following statement regarding helium is incorrect?

• It is used to fill gas balloons instead of hydrogen because it is lighter and non – inflammable

• It is used in gas – cooled nuclear reactors

• It is used to produce and sustain powerful superconducting reagents

• It is used to produce and sustain powerful superconducting reagents