Chemical Kinetics

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

The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the

1. rate is proportional to the surface coverage
2. rate is inversely proportional to the surface coverage
3. rate is independent of the surface coverage
4. rate of decomposition is very slow.

The rate constant of the reaction A B is 0.6 10-3 mol L-1 s-1. If the concentration of A is 5 M, then concentration of B after 20 minutes is

1. 3.60 M
2. 0.36 M
3. 0.72 M
4. 1.08 M

The activation energy of a reaction can be determined from the slope of which of the following graphs?

1. k vs. 1T
2. T k vs. 1T
3. k vs. T
4. kT vs. T

When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is

1. second
2. more than zero but less than first
3. zero
4. first.

A reaction having equal energies of activation for forward and reverse reactions has

1. H = 0
2. H = G = S = 0
3. S = 0
4. G = 0

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20 C to 35 C? (R = 8.314 J mol-1 K-1)

1. 34.7 kJ mol-1
2. 15.1 kJ mol-1
3. 342 kJ mol-1
4. 269 kJ mol-1

For a reaction between A and B the order with respect to A is 2 and the order with respect to B is 3. The concentrations of both A and B are doubled, the rate will increase by a factor of

1. 12
2. 16
3. 32
4. 10

A reaction is 50\% complete in 2 hours and 75\% complete in 4 hours. The order of reaction is

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

Activation energy (Ea) and rate constants (k1 and k2) of a chemical reaction at two different temperatures (T1 and T2) are related by

1. k2k1 = - EaR ( 1T1 - 1T2 )
2. k2k1 = - EaR ( 1T2 - 1T1 )
3. k2k1 = - EaR ( 1T2 + 1T1 )
4. k2k1 = EaR ( 1T1 - 1T2 )

In a reaction, A + B product, rate is doubled when the concentration of B is doubled, and rate increases by a factor of 8 when the concentrations of both the reactants (A and B) are doubled, rate law for the reaction can be written as

1. rate = k[A][B]2
2. rate = k[A]2[B]2
3. rate = k[A][B]
4. rate = k[A]2[B]

In a zero-order reaction, for every 10 rise of temperature, the rate is doubled. If the temperature is increased from 10 to 100 , the rate of the reaction will become

1. 256 times
2. 512 times
3. 64 times
4. 128 times

The rate of the reaction: 2N2O5 4NO2 + O2 can be written in three ways. -d[N2O5]dt = k [N2O5] d[NO2]dt = k' [N2O5]; d[O2]dt = k'' [N2O5] The relationship between k and k' and between k and k'' are

1. k' = 2k; k'' = k
2. k' = 2k; k'' = k/2
3. k' = 2k; k'' = 2k
4. k' = k; k'' = k

The unit of rate constant for a zero order reaction is

1. mol L-1 s-1
2. L mol-1 s-1
3. L2 mol-2 s-1
4. s-1

The half-life of a substance in a certain enzyme-catalysed reaction is 138 s. The time required for the concentration of the substance to fall from 1.28 mg L-1 to 0.04 mg L-1 is

1. 414 s
2. 552 s
3. 690 s
4. 276 s

Which one of the following statements for the order of a reaction is incorrect?

1. Order can be determined only experimentally.
2. Order is not influenced by stoichiometric coefficient of the reactants.
3. Order of a reaction is sum of power to the concentration terms of reactants to express the rate of reaction.
4. Order of reaction is always whole number.

The rate of the reaction, 2NO + Cl2 2NOCl is given by the rate equation rate = k[NO]2[Cl2]. The value of the rate constant can be increased by

1. increasing the temperature
2. increasing the concentration of NO
3. increasing the concentration of the Cl2
4. doing all of these.

For an endothermic reaction, energy of activation is Ea and enthalpy of reaction is H (both of these in kJ/mol). Minimum value of Ea will be

1. less than H
2. equal to H
3. more than H
4. equal to zero

For the reaction N2O5(g) 2NO2(g) + 12O2(g) the value of rate of disappearance of N2O5 is given as 6.25 10-3 mol L-1 s-1. The rate of formation of NO2 and O2 is given respectively as

1. 6.25 10-3 mol L-1 s-1 and 6.25 10-3 mol L-1 s-1
2. 1.25 10-2 mol L-1 s-1 and 3.125 10-3 mol L-1 s-1
3. 6.25 10-3 mol L-1 s-1 and 3.125 10-3 mol L-1 s-1
4. 1.25 10-2 mol L-1 s-1 and 6.25 10-3 mol L-1 s-1

During the kinetic study of the reaction, 2A + B C + D, following results were obtained array|l|l|l|l| Run & [A]/ mol L-1 & [B]/ mol L-1 & Initial rate of formation \ & & & of D/ mol L-1 min-1 \ I. & 0.1 & 0.1 & 6.0 10-3 \ II. & 0.3 & 0.2 & 7.2 10-2 \ III. & 0.3 & 0.4 & 2.88 10-1 \ IV. & 0.4 & 0.1 & 2.40 10-2 \ array Based on the above data which one of the following is correct?

1. Rate = k[A]2[B]
2. Rate = k[A][B]
3. Rate = k[A]2[B]2
4. Rate = k[A][B]2

For the reaction, N2 + 3H2 2NH3, if d[NH3]dt = 2 10-4 mol L-1 s-1, the value of -d[H2]dt would be

1. 4 10-4 mol L-1 s-1
2. 6 10-4 mol L-1 s-1
3. 1 10-4 mol L-1 s-1
4. 3 10-4 mol L-1 s-1

In the reaction, BrO-3(aq) + 5Br-(aq) + 6H+ 3Br2(l) + 3H2O(l). The rate of appearance of bromine (Br2) is related to rate of disappearance of bromide ions as

1. d[Br2]dt = - 53 d[Br-]dt
2. d[Br2]dt = 53 d[Br-]dt
3. d[Br2]dt = 35 d[Br-]dt
4. d[Br2]dt = - 35 d[Br-]dt

Half-life period of a first order reaction is 1386 s. The specific rate constant of the reaction is

1. 0.5 10-2 s-1
2. 0.5 10-3 s-1
3. 5.0 10-2 s-1
4. 5.0 10-3 s-1

For the reaction A + B products, it is observed that (i) on doubling the initial concentration of A only, the rate of reaction is also doubled and (ii) on doubling the initial concentration of both A and B, there is a change by a factor of 8 in the rate of the reaction. The rate of this reaction is given by

1. rate = k[A]2[B]2
2. rate = k[A][B]2
3. rate = k[A][B]
4. rate = k[A]2[B]

The rate constants k1 and k2 for two different reactions are 1016 e-2000/T and 1015 e-1000/T, respectively. The temperature at which k1 = k2 is

1. 2000 K
2. 10002.303 K
3. 1000 K
4. 20002.303 K

The bromination of acetone that occurs in acid solution is represented by this equation. CH3COCH3(aq) + Br2(aq) CH3COCH2Br(aq) + H+(aq) + Br-(aq) These kinetic data were obtained for given reaction concentrations. array|c|c|c|c| [CH3COCH3], M & [Br2], M & [H+], M & Initial rate, disappearance of Br2, M s-1 \ 0.30 & 0.05 & 0.05 & 5.7 10-5 \ 0.30 & 0.10 & 0.05 & 5.7 10-5 \ 0.30 & 0.10 & 0.10 & 1.2 10-4 \ 0.40 & 0.05 & 0.20 & 3.1 10-4 \ array Based on these data, the rate equation is

1. Rate = k[CH3COCH3][Br2][H+]2
2. Rate = k[CH3COCH3][Br2][H+]
3. Rate = k[CH3COCH3][H+]
4. Rate = k[CH3COCH3][Br2]

If 60% of a first order reaction was completed in 60 minutes, 50% of the same reaction would be completed in approximately (log 4 = 0.60, log 5 = 0.70)

1. 45 minutes
2. 60 minutes
3. 40 minutes
4. 50 minutes

In a first-order reaction A B, if k is rate constant and initial concentration of the reactant A is 0.5 M, then the half-life is

1. 2k
2. 2k 0.5
3. 2k
4. 0.6930.5k

The reaction of hydrogen and iodine monochloride is given as: H2(g) + 2ICl(g) 2HCl(g) + I2(g) This reaction is of first order with respect to H2(g) and ICl(g). The following mechanisms were proposed. Mechanism A: H2(g) + 2ICl(g) 2HCl(g) + I2(g) Mechanism B: H2(g) + ICl(g) HCl(g) + HI(g); slow HI(g) + ICl(g) HCl(g) + I2(g); fast Which of the above mechanism(s) can be consistent with the given information about the reaction?

1. A and B both
2. Neither A nor B
3. A only
4. B only

Consider the reaction : N2(g) + 3H2(g) 2NH3(g) The equality relationship between d[NH3]dt and - d[H2]dt is

1. d[NH3]dt = - d[H2]dt
2. d[NH3]dt = - 13 d[H2]dt
3. + d[NH3]dt = - 23 d[H2]dt
4. + d[NH3]dt = - 32 d[H2]dt