Chemical Kinetics · Question 25

Pre-exponential factors of two different reactions of same order are identical. Let activation energy of first reaction exceed the activation energy of second reaction by 20 kJ mol-1. If k1 and k2 are the rate constants of first and second reaction respectively at 300 K, then k2k1 will be . (nearest integer) [R = 8.3 J K-1 mol-1]

Decomposition of A is a first order reaction at T(K) and is given by A(g) B(g) + C(g). In a closed 1 L vessel, 1 bar A(g) is allowed to decompose at T(K). After 100 minutes, the total pressure was 1.5 bar. What is the rate constant (in min-1) of the reaction? ( 2 = 0.3)

1. 6.9 10-4
2. 6.9 10-3
3. 6.9 10-1
4. 6.9 10-2

In a first order decomposition reaction, the time taken for the decomposition of reactant to one fourth and one eighth of its initial concentration are t1 and t2 (s), respectively. The ratio t1/t2 will be:

1. 43
2. 32
3. 34
4. 23

A person's wound was exposed to some bacteria and then bacterial growth started to happen at the same place. The wound was later treated with some antibacterial medicine and the rate of bacterial decay (r) was found to be proportional with the square of the existing number of bacteria at any instance. Which of the following set of graphs correctly represents the 'before' and 'after' situation of the application of the medicine? [Given: N = No. of bacteria, t = time, bacterial growth follows 1st order kinetics.]

1. [figure]
2. [figure]
3. [figure]
4. [figure]

Reaction A(g) 2B(g) + C(g) is a first order reaction. It was started with pure A. array|c|c| t/min & Pressure of system at time t/mm Hg \ 10 & 160 \ & 240 \ array Which of the following option is incorrect?

1. Initial pressure of A is 80 mm Hg
2. The reaction never goes to completion
3. Partial pressure of A after 10 minutes is 40 mm Hg
4. Rate constant of the reaction is 1.693 min-1

A(g) B(g) + C(g) is a first order reaction. array|l|c|c| Time & t & \ Psystem & Pt & P \ array The reaction was started with reactant A only. Which of the following expressions is correct for rate constant k?

1. k = 1t P Pt
2. k = 1t P 2(P - Pt)
3. k = 1t 2(P - Pt)Pt
4. k = 1t P (P - Pt)

For A2 + B2 2AB Ea for forward and backward reaction are 180 and 200 kJ mol-1 respectively. If catalyst lowers Ea for both reactions by 100 kJ mol-1. Which of the following statement is correct?

1. Catalyst does not alter the Gibbs energy change of a reaction.
2. The enthalpy change for the reaction is +20 kJ mol-1.
3. Catalyst can cause non-spontaneous reactions to occur.
4. The enthalpy change for the catalysed reaction is different from that of uncatalysed reaction.

Rate law for a reaction between A and B is given by r = k[A]n[B]m If concentration of A is doubled and concentration of B is halved from their initial value, the ratio of new rate of reaction to the initial rate of reaction ( r2r1 ) is

1. (n-m)
2. 2(n-m)
3. 12m+n
4. (m+n)

Consider the following plots of log of rate constant k (log k) vs 1T for three different reactions. The correct order of activation energies of these reactions is : [figure]

1. Ea2 > Ea1 > Ea3
2. Ea1 > Ea3 > Ea2
3. Ea3 > Ea2 > Ea1
4. Ea1 > Ea2 > Ea3

Half life of zero order reaction A product is 1 hour, when initial concentration of reactant is 2.0 mol L-1. The time required to decrease concentration of A from 0.50 to 0.25 mol L-1 is :

1. 0.5 hour
2. 15 min
3. 60 min
4. 4 hour