Chemical kinetics questions

1

UNIT 9
CHEMICAL KINETICS
1.

(c) mole 1–1 sec–1

The rate law for a reaction
A + B →products, is rate = k [A]1[B]2.

7.

Then, which one of the following statements is false ?
(a) If [B] is held constant while [A] is doubled, the reaction will proceed twice as fast.
(b) If [A] is held constant while [B] is reduced to one quarter, the rate will be halved (c) If [A] and [B] are both doubled, the reaction will proceed 8 times as fast.
2.

Fro a first order reaction, a straight line is obtained if you plot
(a) log Conc Vs time
(b) Conc. Vs time
(c)

3.

4.

1
Conc

For a given first order reaction, it takes 20 minutes for the reaction to drop from 1.0 M to 0.60 M. The time required for the concentration to drop from 0.60 M to 0.36
M will be
(a) more than 20 minutes
(b) 20 minutes
(c) less than 20 minutes
(d) none of these
For a certain decomposition, the rate is 0.30
M sec–1 when the concentration of reactant is 0.20 M. If the reaction is second order, the rate (in M sec–1) when concentration is increased 3-fold is
(a) 0.30
(b) 0.90
(c) 0.60
(d) 2.70

5.

A 10º rise in temperature doubles the rate of reaction. This is because more molecules obtain (a) activation energy
(b) a catalyst
(c) a new reaction path
(d) the rate-determining step

6.

The unit for rate constant of a zero order reaction is
(a) sec–1
(b) 1 mole–1 sec–1

For a given reaction, the rate constant at
37ºC is twice that at 27ºC, its energy of activation in Joules is computed at
(a) log


1
Ea
 10
=
 300 × 310 
2 2.303 × 8.31 



 10
 300 × 310 


1
Ea
10
(c) log =
×
2 2.303 × 8.31 27 × 37
2
Ea
10
(d) =
1
2.303 × 8.31 300 × 310

(b) log

1
Ea
=
2 2.303 × 8.31

8.

In arrhenius equation, the fraction of effective collisions is given by
(a) k =A e–Ea/RT
(b) A
(c) e–Ea/RT
(d) none of these

9.

Quantum yield of a photochemical reaction is given by

1
Vs time
Conc