1

### AIPMT 2003

If the rate of the reaction is equal to the rate constant, the order of the reaction is
A
0
B
1
C
2
D
3

## Explanation

As r = k[A]n

if n = 0

r = k[A]0

or r = k thus for zero order reactions rate is equal to the rate constant.
2

### AIPMT 2003

The temperature dependence of rate constant (k) of a chemical reaction is written in terms of Arrhenius equation, $k = A \cdot {e^{ - E{}^ * /RT}}$. Activation energy (E$*$) of the reaction can be calculated by plotting
A
$k\,\,vs\,\,T$
B
$k\,\,vs\,\,{1 \over {\log T}}$
C
$\log \,k\,\,vs\,\,{1 \over T}$
D
$\log \,k\,\,vs\,{1 \over {\log T}}$

## Explanation

Arrhenius equation k = $A{e^{ - {{{E_a}} \over {RT}}}}$

$\Rightarrow$ log k = log A - ${{{{E_a}} \over {2.303RT}}}$

Comparing it with equation of straight line i.e.,

y = mx + C

On plotting log k vs ${1 \over T}$, we get a straight line, the slope indicates the value of activation energy.
3

### AIPMT 2002

2A $\to$ B + C

It would be a zero order reaction when
A
the rate of reaction is proportional to square of concentration of A
B
The rate of reaction remains same at any concentration of A
C
the rate remains unchanged at any concentration of B and C
D
the rate of reaction doubles if concentrations of B is increased to double.

## Explanation

2A $\to$ B + C

If it is zero order reaction r = k [A]o.

i.e the rate remains same at any concentration of 'A'. i.e independent upon concentration of A.
4

### AIPMT 2001

For the reaction;

2N2O5 $\to$ 4NO2 + O2 rate and rate constant are 1.02 $\times$ 10$-$4 and 3.4 $\times$ 10$-$5 sec$-$1 respectively, then concentration of N2O5 at that time will be
A
1.732
B
3
C
1.02 $\times$ 10$-$4
D
3.4 $\times$ 105

## Explanation

For the reaction;

2N2O5 $\to$ 4NO2 + O2

This is a first order reaction.

$\therefore$ rate = k [N2O5] ;

[N2O5] = ${{rate} \over k}$

= ${{1.02 \times {{10}^{ - 4}}} \over {3.4 \times {{10}^{ - 5}}}}$

= 3

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