Chemical Kinetics

Mechanism of a hypothetical reaction X2 + Y2 2XY, is given below : (i) X2 X + X (fast) (ii) X + Y2 XY + Y (slow) (iii) X + Y XY (fast) The overall order of the reaction will be

1. 2
2. 0
3. 1.5
4. 1

A first order reaction has a specific reaction rate of 10-2 sec-1. How much time will it take for 20 g of the reactant to reduce to 5 g?

1. 138.6 sec
2. 346.5 sec
3. 693.0 sec
4. 238.6 sec

The rate of first-order reaction is 0.04 mol L-1 s-1 at 10 seconds and 0.03 mol L-1 s-1 at 20 seconds after initiation of the reaction. The half-life period of the reaction is

1. 44.1 s
2. 54.1 s
3. 24.1 s
4. 34.1 s

The addition of a catalyst during a chemical reaction alters which of the following quantities?

1. Enthalpy
2. Activation energy
3. Entropy
4. Internal energy

The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the

1. rate is proportional to the surface coverage
2. rate is inversely proportional to the surface coverage
3. rate is independent of the surface coverage
4. rate of decomposition is very slow.

The rate constant of the reaction A B is 0.6 10-3 mol L-1 s-1. If the concentration of A is 5 M, then concentration of B after 20 minutes is

1. 3.60 M
2. 0.36 M
3. 0.72 M
4. 1.08 M

The activation energy of a reaction can be determined from the slope of which of the following graphs?

1. k vs. 1T
2. T k vs. 1T
3. k vs. T
4. kT vs. T

When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is

1. second
2. more than zero but less than first
3. zero
4. first.

A reaction having equal energies of activation for forward and reverse reactions has

1. H = 0
2. H = G = S = 0
3. S = 0
4. G = 0

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20 C to 35 C? (R = 8.314 J mol-1 K-1)

1. 34.7 kJ mol-1
2. 15.1 kJ mol-1
3. 342 kJ mol-1
4. 269 kJ mol-1