Chemical Kinetics · Question 23

If the rate constant for a first order reaction is k, the time (t) required for the completion of 99 % of the reaction is given by :

1. t = 4.606k
2. t = 2.303k
3. t = 0.693k
4. t = 6.909k

For the chemical reaction N2(g) + 3H2(g) 2NH3(g) the correct option is :

1. - d[N2]dt = 2 d[NH3]dt
2. - d[N2]dt = 12 d[NH3]dt
3. 3 d[H2]dt = 2 d[NH3]dt
4. - 13 d[H2]dt = - 12 d[NH3]dt

The correct difference between first and second order reactions is that

1. the rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations
2. the half-life of a first-order reaction does not depend on [A]0; the half-life of a second order reaction does depend on [A]0
3. a first-order reaction can be catalysed; a second-order reaction cannot be catalysed
4. the rate of a first-order reaction does depend on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations

When initial concentration of the reactant is doubled, the half-life period of a zero order reaction

1. is halved
2. is doubled
3. is tripled
4. remains unchanged.

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