Chemical Kinetics

Given below are two statements : R = 8.314 J K-1 mol-1 and 1 cal = 4.2 J In the light of the above statements, choose the correct answer from the options given below :

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

First order gas phase reaction A B + C pi = initial pressure of gas A, pt = total pressure of the reaction mixture at time t Expression of rate constant (k) is

1. 1t pi2pi - pt
2. 1t 2pipi - pt
3. 1t pi3pi - 2pt
4. 1t 3pi4pi - pt

Consider the first order reaction R P. The fraction of molecules decomposed in the given first order reaction can be expressed as

1. 1 - ek1t
2. 1 + ek1t
3. 1 + e-k1t
4. 1 - e-k1t

Consider the given graph showing variation of reactant concentration with time. Three different reactions were started with identical initial concentration of reactants. Which of the following statement is correct? [figure]

1. The order of all the three reactions is same.
2. The rate constant of reaction 3 is larger than the rate constant of reaction 2 if the order of reaction is same for both.
3. The SI unit of rate constant of reaction 1 is s-1.
4. Thermal decomposition of HI on gold surface is an example of reaction 2.

t100\% is the time required for the 100% completion of the reaction while t1/2 is the time required for 50% of the reaction to be completed. Which of the following option correctly represents the relation between t100\% and t1/2 for zero and first order reactions respectively ?

1. t100\% = (t1/2)2 and t100\% = (t1/2)-
2. t100\% = 2t1/2 and t100\% = (t1/2)
3. t100\% = 2t1/2 and t100\% = (2t1/2)2
4. t100\% = (t1/2) and t100\% = 2t1/2

Consider the reaction aX bY, for which the rate constant at 30°C is 1 10-3 mol-1 L s-1. Which of the following statements are true? Choose the correct answer from the options given below:

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

An organic compound undergoes first order decomposition. The time taken for decomposition to ( 18 )th and ( 110 )th of its initial concentration are t1/8 and t1/10 respectively. What is the value of t1/8 t1/10 10? ( 2 = 0.3)

1. 30
2. 9
3. 3
4. 0.9

A D is an endothermic reaction occurring in three steps (elementary). (i) A B, Hi = +ve (ii) B C, Hii = -ve (iii) C D, Hiii = -ve Which of the following graphs between potential energy (y-axis) vs reaction coordinate (x-axis) correctly represents the reaction profile of A D?

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

At 27 in presence of a catalyst, activation energy of a reaction is lowered by 10 kJ mol-1. The logarithm of ratio of k (catalysed)k (uncatalysed) is.... (Consider that the frequency factor for both the reactions is same)

1. 1.741
2. 0.1741
3. 17.41
4. 3.482

[figure] Given above is the concentration vs time plot for a dissociation reaction : A nB. Based on the data of the initial phase of the reaction (initial 10 min), the value of n is .

1. 2
2. 5
3. 4
4. 3

Observe the following reactions at T(K). I. A products. II. 5Br-(aq) + BrO3-(aq) + 6H+(aq) 3Br2(aq) + 3H2O(l) Both the reactions are started at 10.00 am. The rates of these reactions at 10.10 am are same. The value of - [Br-] t at 10.10 am is 2 10-4 mol L-1 min-1. The concentration of A at 10.10 am is 10-2 mol L-1. What is the first order rate constant (in min-1) of reaction I?

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

A product (First order reaction). Three sets of experiments were performed for a reaction under similar experimental conditions: Run 1 100 mL of 10 M solution of reactant A Run 2 200 mL of 10 M solution of reactant A Run 3 100 mL of 10 M solution of reactant A + 100 mL of H2O added. The correct variation of rate of reaction is

1. Run 1 = Run 2 = Run 3
2. Run 3 < Run 1 < Run 2
3. Run 1 < Run 2 < Run 3
4. Run 3 < Run 1 = Run 2

Correct statements regarding Arrhenius equation among the following are : Choose the correct answer from the options given below :

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

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

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

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]

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]