Chemical Kinetics

For a certain reaction R → Product, the plot of concentration [R] vs time has a negative slope as shown. The order of reaction is : [figure]

1. 1
2. 2.5
3. 2
4. 0

Given below is an expression for the rate constant of a first-order reaction occurring at a certain temperature, T (K). ln k = 14.34 − 1.25 104T The energy of activation in kcal mol-1 for the reaction is : (Given : k in s-1, R = 1.987 cal mol-1 K-1)

1. 12.42
2. 18.63
3. 14.34
4. 24.84

For an elementary chemical reaction, the Arrhenius plot is given below. [figure] If the energy of activation is 6.64 kJ mol-1 and R = 8.3 J K-1 mol-1, the temperature at which the rate constant becomes e2 min-1, is

1. 250 K
2. 125 K
3. 150 K
4. 200 K

2A k B is a zero-order reaction, where k = 1.0 mol L-1 min-1. If the initial concentration of A is 2 M, then the time taken to complete 75\% of the reaction will be

1. 2.0 min
2. 1.5 min
3. 0.75 min
4. 1.0 min

If the rate constant of a reaction is 0.03 s-1, how much time does it take for 7.2 mol L-1 concentration of the reactant to get reduced to 0.9 mol L-1 ? (Given: 2 = 0.301)

1. 210 s
2. 21.0 s
3. 69.3 s
4. 23.1 s

If the half-life (t1/2) for a first order reaction is 1 minute, then the time required for 99.9\% completion of the reaction is closest to :

1. 5 minutes
2. 10 minutes
3. 2 minutes
4. 4 minutes

Activation energy of any chemical reaction can be calculated if one knows the value of

1. rate constant at standard temperature
2. probability of collision
3. orientation of reactant molecules during collision
4. rate constant at two different temperatures

Which plot of k vs 1T is consistent with Arrhenius equation?

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

The rate of a reaction quadruples when temperature changes from 27 to 57 . Calculate the energy of activation. Given R = 8.314 J K-1 mol-1, 4 = 0.6021

1. 38.04 kJ/mol
2. 380.4 kJ/mol
3. 3.80 kJ/mol
4. 3804 kJ/mol

Following data is for a reaction between reactants A and B : array|c|c|c| Rate ( mol L-1 s-1) & [A] & [B] \ 2 10-3 & 0.1 M & 0.1 M \ 4 10-3 & 0.2 M & 0.1 M \ 1.6 10-2 & 0.2 M & 0.2 M \ array The order of the reaction with respect to A and B, respectively, are

1. 1, 0
2. 0, 1
3. 1, 2
4. 2, 1

Which of the following plot represents the variation of k versus 1T in accordance with Arrhenius equation?

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

Rate constants of a reaction at 500 K and 700 K are 0.04 s-1 and 0.14 s-1, respectively; then, activation energy of the reaction is : (Given: 3.5 = 0.5441, R = 8.31 J K-1 mol-1)

1. 182310 J
2. 18500 J
3. 18219 J
4. 18030 J

For a certain reaction, the rate = k[A]2[B], when the initial concentration of A is tripled keeping concentration of B constant, the initial rate would

1. increase by a factor of six
2. increase by a factor of nine
3. increase by a factor of three
4. decrease by a factor of nine

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. In the light of the above statements, choose the correct answer from the options given below:

1. Both A and R are true but R is NOT the correct explanation of A.
2. A is true but R is false.
3. A is false but R is true.
4. Both A and R are true and R is the correct explanation of A.

The given graph is a representation of kinetics of a reaction [figure] The y and x axes for zero and first order reactions, respectively are

1. zero order (y = concentration and x = time), first order (y = t1/2 and x = concentration)
2. zero order (y = concentration and x = time), first order (y = rate constant and x = concentration)
3. zero order (y = rate and x = concentration), first order (y = t1/2 and x = concentration)
4. zero order (y = rate and x = concentration), first order (y = rate and x = t1/2)

For a first order reaction A Products, initial concentration of A is 0.1 M, which becomes 0.001 M after 5 minutes. Rate constant for the reaction in min-1 is

1. 1.3818
2. 0.9212
3. 0.4606
4. 0.2303

The half life of a first order reaction is 2000 years. If the concentration after 8000 years is 0.02 M, then the initial concentration was :

1. 0.04 M
2. 0.16 M
3. 0.32 M
4. 0.08 M

For a chemical reaction 4A + 3B 6C + 9D Rate of formation of C is 6 10-2 mol L-1 s-1 and rate of disappearance of A is 4 10-2 mol L-1 s-1. The rate of reaction and amount of B consumed in interval of 10 seconds, respectively will be :

1. 10 10-2 mol L-1 s-1 and 30 10-2 mol L-1
2. 1 10-2 mol L-1 s-1 and 30 10-2 mol L-1
3. 10 10-2 mol L-1 s-1 and 10 10-2 mol L-1
4. 1 10-2 mol L-1 s-1 and 10 10-2 mol L-1

For a reaction, A B, enthalpy of reaction is -4.2 kJ mol-1 and enthalpy of activation is 9.6 kJ mol-1. The correct potential energy profile for the reaction is shown in option.

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

The slope of Arrhenius plot ( ln k v/s 1T ) of first order reaction is -5 103 K. The value of Ea of the reaction is. Choose the correct option for your answer. [Given R = 8.314 J K-1 mol-1]

1. -83 kJ mol-1
2. 41.5 kJ mol-1
3. 83.0 kJ mol-1
4. 166 kJ mol-1

An increase in the concentration of the reactants of a reaction leads to change in :

1. heat of reaction
2. threshold energy
3. collision frequency
4. activation energy

The rate constant for a first order reaction is 4.606 10-3 s-1. The time required to reduce 2.0 g of the reactant to 0.2 g is :

1. 200 s
2. 500 s
3. 1000 s
4. 100 s

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