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1

AIPMT 2003

MCQ (Single Correct Answer)
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

MCQ (Single Correct Answer)
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

MCQ (Single Correct Answer)
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

MCQ (Single Correct Answer)
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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