Chemical Kinetics

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

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

Drug X becomes ineffective after 50\% decomposition. The original concentration of drug in a bottle was 16 mg/mL which becomes 4 mg/mL in 12 months. The expiry time of the drug in months is . Assume that the decomposition of the drug follows first order kinetics.

1. 12
2. 3
3. 6
4. 2

array|c|c| [A]0/ mol L-1 & t1/2/min \ 0.100 & 200 \ 0.025 & 100 \ array For a given reaction R P, t1/2 is related to [A]0 as given in table. Given: 2 = 0.30 Which of the following is true? Choose the correct answer from the options given below:

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

Consider an elementary reaction A(g) + B(g) C(g) + D(g) If the volume of reaction mixture is suddenly reduced to 13 of its initial volume, the reaction rate will become 'x' times of the original reaction rate. The value of x is :

1. 3
2. 9
3. 13
4. 19

For bacterial growth in a cell culture, growth law is very similar to the law of radioactive decay. Which of the following graphs is most suitable to represent bacterial colony growth? Where N - Number of bacteria at any time, N0 - Initial number of bacteria.

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

For a reaction, N2O5(g) 2NO2(g) + 12O2(g) in a constant volume container, no products were present initially. The final pressure of the system when 50\% of reaction gets completed is

1. 5/2 times of initial pressure
2. 7/2 times of initial pressure
3. 7/4 times of initial pressure
4. 5 times of initial pressure

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

1. Both Statement I and Statement II are false
2. Statement I is true but Statement II is false
3. Statement I is false but Statement II is true
4. Both Statement I and Statement II are true

Consider a complex reaction taking place in three steps with rate constants k1, k2 and k3 respectively. The overall rate constant k is given by the expression k= k1k3k2. If the activation energies of the three steps are 60, 30 and 10 kJ mol-1 respectively, then the overall energy of activation in kJ mol-1 is . (Nearest integer)

For the thermal decomposition of N2O5(g) at constant volume, the following table can be formed, for the reaction mentioned below. 2N2O5(g) 2N2O4(g)+O2(g) [figure] x= 10-3 atm [nearest integer] Given : Rate constant for the reaction is 4.606 10-2 s-1.

Which of the following graphs most appropriately represents a zero order reaction?

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

A B The molecule A changes into its isomeric form B by following a first order kinetics at a temperature of 1000 K. If the energy barrier with respect to reactant energy for such isomeric transformation is 191.48 kJ mol-1 and the frequency factor is 1020, the time required for 50\% molecules of A to become B is picoseconds (nearest integer). [R=8.314 J K-1 mol-1 ]

Which of the following statement is not true for radioactive decay?

1. Half life is 2 times of 1rate constant.
2. Decay constant increases with increase in temperature.
3. Decay constant does not depend upon temperature.
4. Amount of radioactive substance remained after three half lives is 18th of original amount.

Consider the given figure and choose the correct option : [figure]

1. Activation energy of both forward and backward reaction is E1 + E2 and reactant is more stable than product.
2. Activation energy of forward reaction is E1 + E2 and product is more stable than reactant.
3. Activation energy of backward reaction is E1 and product is more stable than reactant.
4. Activation energy of forward reaction is E1 + E2 and product is less stable than reactant.

Given below are two statements : Statement I : The rate law for the reaction A + B C is rate (r) = k[A]2[B]. When the concentration of both A and B is doubled, the reaction rate is increased "x" times. Statement II : [figure] The figure is showing "the variation in concentration against time plot" for a "y" order reaction. The value of x + y is .

Consider the following first order gas phase reaction at constant temperature A(g) 2B(g) + C(g) If the total pressure of the gases is found to be 200 torr after 23 sec. and 300 torr upon the complete decomposition of A after a very long time, then the rate constant of the given reaction is 10-2 s-1 (nearest integer) [Given : 10(2) = 0.301]

Consider the following reaction A + B C The time taken for A to become 1/4th of its initial concentration is twice the time taken to become 1/2 of the same. Also, when the change of concentration of B is plotted against time, the resulting graph gives a straight line with a negative slope and a positive intercept on the concentration axis. The overall order of the reaction is .

For a reaction A K1 B K2 C. If the rate of formation of B is set to be zero then the concentration of B is given by :

1. (K1 - K2)[A]
2. (K1 + K2)[A]
3. K1K2[A]
4. (K1/K2)[A]

Time required for 99.9\% completion of a first order reaction is times the time required for completion of 90\% reaction.(nearest integer)

Consider the two different first order reactions given below A + B C (Reaction 1) P Q (Reaction 2) The ratio of the half life of Reaction 1 : Reaction 2 is 5 : 2. If t1 and t2 represent the time taken to complete 2/3rd and 4/5th of Reaction 1 and Reaction 2, respectively, then the value of the ratio t1 : t2 is 10-1 (nearest integer). [Given : 10(3) = 0.477 and 10(5) = 0.699]

During kinetic study of reaction 2A + B C + D, the following results were obtained : [figure] Based on above data, overall order of the reaction is .