Chemical Kinetics · Question 31

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

In a reaction A + B C, initial concentrations of A and B are related as [A]0 = 8[B]0. The half-lives of A and B are 10 min and 40 min, respectively. If they start to disappear at the same time, both following first order kinetics, after how much time will the concentration of both the reactants be same?

1. 20 min
2. 40 min
3. 80 min
4. 60 min

Consider the following statements related to temperature dependence of rate constants. Identify the correct statements. Choose the correct answer from the options given below:

1. A, C and D Only
2. B, D and E Only
3. B and C Only
4. A and B Only

For the reaction A products. [figure] The concentration of A at 10 minutes is 10-3 mol L-1 (nearest integer). The reaction was started with 2.5 mol L-1 of A.

Reactant A converts to product D through the given mechanism (with the net evolution of heat): A B slow; H = +ve B C fast; H = -ve C D fast; H = -ve Which of the following represents the above reaction mechanism?

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

For the reaction A B the following graph was obtained. The time required (in seconds) for the concentration of A to reduce to 2.5 g L-1 (if the initial concentration of A was 50 g L-1) is . (Nearest integer) Given : 2 = 0.3010 [figure]

The reaction A2 + B2 2AB follows the mechanism: A2 k-1 k1 A + A (fast) A + B2 k2 AB + B (slow) A + B AB (fast) The overall order of the reaction is:

1. 3
2. 2.5
3. 1.5
4. 2