AIPMT 2011 Mains

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MCQ (Single Correct Answer)

The rate of the reaction : 2N₂O₅ $$ \to $$ 4NO₂ + O₂
can be written in three ways.

$${{ - d\left[ {{N_2}{O_5}} \right]} \over {dt}} = k\left[ {{N_2}{O_5}} \right]$$

$${{d\left[ {N{O_2}} \right]} \over {dt}} = k'\left[ {{N_2}{O_5}} \right];\,\,$$ $${{d\left[ {{O_2}} \right]} \over {dt}} = k''\left[ {{N_2}{O_5}} \right]$$

The relationship between k and k' and between k and k'' are

$$k' = 2k ; k'' = k$$

$$k' = 2k ; k'' = k/2$$

$$k' = 2k ; k'' = 2k$$

$$k' = k ; k'' = k$$

Explanation

Rate of disappearance of reactants = Rate of appearance of products

$$ - {1 \over 2}$$$${{ - d\left[ {{N_2}{O_5}} \right]} \over {dt}}$$ = $${1 \over 4}$$$${{d\left[ {N{O_2}} \right]} \over {dt}}$$ = $${{d\left[ {{O_2}} \right]} \over {dt}}$$

$$ \Rightarrow $$ $${1 \over 2}$$$$k\left[ {{N_2}{O_5}} \right]$$ = $${1 \over 4}$$$$k'\left[ {{N_2}{O_5}} \right]$$ = $$k''\left[ {{N_2}{O_5}} \right]$$

$$ \Rightarrow $$ $${k \over 2} = {{k'} \over 4} = k''$$

$$ \Rightarrow $$ $$k' = 2k ; k'' = k/2$$

AIPMT 2011 Prelims

MCQ (Single Correct Answer)

Which one of the following statements for the order of a reaction is incorrect?

Order can be determined only experimentally.

Order is not influenced by stoichiometric coefficient of the reactants.

Order of a reaction is sum of power to the concentration terms of reactants to express the rate of reaction.

Order of reaction is always whole number.

Explanation

Order of a reaction is not always whole number. It can be zero, or fractional also.

AIPMT 2010 Prelims

MCQ (Single Correct Answer)

During the kinetic study of the reaction, 2A + B $$ \to $$ C + D, following results were obtained

Run	[A]/mol L^$$-$$1	[B]/mol L^$$-$$1	Initial rate of formation of D/mol L^$$-$$1 min^$$-$$1
I.	0.1	0.1	6.0$$ \times $$10^$$-$$3
II.	0.3	0.2	7.2$$ \times $$10^$$-$$2
III.	0.3	0.4	2.88$$ \times $$10^$$-$$1
IV.	0.4	0.1	2.40$$ \times $$10^$$-$$2

Based on the above data which one of the following is correct?

Rate = k[A]²[B]

Rate = k[A][B]

Rate = k[A]²[B]²

Rate = k[A][B]²

Explanation

Rate = k[A]^x [B]^y

For the given situations

(I) rate = k(0.1)^x (0.1)^y = 6.0$$ \times $$10^$$-$$3

(II) rate = k(0.2)^x (0.3)^y = 7.2$$ \times $$10^$$-$$2

(III) rate = k(0.3)^x (0.4)^y = 2.88$$ \times $$10^$$-$$1

(IV) rate = k(0.4)^x (0.1)^y = 2.40$$ \times $$10^$$-$$2

Dividing eq. (I) by eq. (IV) we get

$${\left( {{{0.1} \over {0.4}}} \right)^x}{\left( {{{0.1} \over {0.1}}} \right)^y} = {{6.0 \times {{10}^{ - 3}}} \over {2.4 \times {{10}^{ - 2}}}}$$

$$ \Rightarrow $$ $${\left( {{1 \over 4}} \right)^x} = {\left( {{1 \over 4}} \right)^1}$$

$$ \Rightarrow $$ x = 1

On dividing eq. (II) by eq. (III) we get

$${\left( {{{0.3} \over {0.3}}} \right)^x}{\left( {{{0.2} \over {0.4}}} \right)^y} = {{7.2 \times {{10}^{ - 2}}} \over {2.88 \times {{10}^{ - 1}}}}$$

$$ \Rightarrow $$ $${\left( {{1 \over 2}} \right)^y} = {1 \over 4}$$

$$ \Rightarrow $$ y = 2

$$ \therefore $$ Rate = k[A][B]²

AIPMT 2010 Mains

MCQ (Single Correct Answer)

The rate of the reaction, 2NO + Cl₂ $$ \to $$ 2NOCl is given by the rate equation rate = k[NO]²[Cl₂]. The value of the rate constant can be increased by

increasing the temperature

increasing the concentration of NO

increasing the concentration of the Cl₂

doing all of these.