1
MCQ (Single Correct Answer)

AIPMT 2015 Cancelled Paper

When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is
A
second
B
more than zero but less than first
C
zero
D
first.

Explanation

Half-life period of a first order reaction is independent of initial concentration,

$${t_{{1 \over 2}}} = {{0.693} \over k}$$
2
MCQ (Single Correct Answer)

AIPMT 2015

The rate constant of the reaction A $$ \to $$ B is 0.6 $$ \times $$ 10$$-$$3 mol L$$-$$1 s$$-$$1. If the concentration of A is 5 M, then concentration of B after 20 minutes is
A
3.60 M
B
0.36 M
C
0.72 M
D
1.08 M

Explanation

For zero order reaction unit of rate constant is mole per second.

$$ \therefore $$ For zero order

x = kt

$$ \Rightarrow $$ x = 0.6 × 10–3 × 20 × 60 = 0.72 M
3
MCQ (Single Correct Answer)

NEET 2013 (Karnataka)

A reaction is 50% complete in 2 hours and 75% complete in 4 hours. The order of reaction is
A
1
B
2
C
3
D
0

Explanation

For a first order reaction,

t75% = 2 $$ \times $$ t50%
4
MCQ (Single Correct Answer)

NEET 2013 (Karnataka)

For a reaction between A and B the order with respect to A is 2 and the other with respect to B is 3. The concentrations of both A and B are doubled, the rate will increase by a factor of
A
12
B
16
C
32
D
10

Explanation

Rate1 = k[A]2[B]3

when concentrations of both A and B are doubled then

Rate2 = k[2A]2[2B]3 = 32 k[A]2[B]3

$$ \therefore $$ Rate will increase by a factor of 32.

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