1

### 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

### 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

### 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

### 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.