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Chemical Kinetics

Short Answer Type

121. For the reaction at 500 K

{NO}_{2} (g) + CO (g) \to {CO}_{2} (g) + NO (g)

The proposed mechanism is as follow:
(i)

{NO}_{2} + {NO}_{2} \to NO + {NO}_{3} (slow) {NO}_{3} + CO \to {CO}_{2} + {NO}_{2} (fast)

Predict the law?

126 Views

Long Answer Type

122. Write the overall reaction and the rate law from the following elementary reactions:

NO + {Br}_{2} ⇋ {NOBr}_{2} (fast) {NOBr}_{2} + NO \to 2 NOBr (slow)

What is the order of the reaction?

130 Views

Short Answer Type

123. Consider the reaction

A \overset{k}{\to} P .

The change in concentration of A with time is shown in the following plot:
(i) Predict the order of reaction.
(ii) Derive the expression for the time required for the completion of the reaction.

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124. Express the rate of the following reaction in terms of disappearance of the reactants and appearance of products:
PCl₅(g) → PCl₃(g) + Cl₂(g)

232 Views

125. Express the rate of the following reaction in terms of disappearance of the reactants and appearance of products:
2NO(g) + O₂(g) → 2NO₂(g)

172 Views

126. Express the rate of the following reaction in terms of disappearance of the reactants and appearance of products:
H₂(g) + l₂(g) → 2HI(g)

146 Views

127. Express the rate of the following reaction in terms of disappearance of the reactants and appearance of products:
CO(g) + NO₂(g) → CO₂(g) + NO(g)

193 Views

128. Express the rate of the following reaction in terms of disappearance of the reactants and appearance of products:
2NO₂(g) + F₂(g) → 2NO₂ F(g)

114 Views

129. The reaction:
2NO + Br₂ → 2NOBr
is supposed to follow the following mechanism.
(i)

NO + {Br}_{2} \overset{fast}{⇌} {NOBr}_{2}

(ii)

{NOBr}_{2} + NO \overset{slow}{\to} 2 NOBr

Suggest the rate law expression.

1259 Views

Long Answer Type

130. Nitric oxide, NO, reacts with oxygen to produce nitrogen dioxide,
2NO(g) + O₂(g) → 2NO₂(g)
What is the predicted rate law, if the mechanism is

The slow step is the rate determining step. In the slow step in this reaction, 1 molecule of NO₃(intermediate) and 1 molecule of NO combine to form the products. Therefore, rate of this reaction depends upon 1 concentration term of NO₃ and 1 concentration term of NO.

∴ Molecularity of the reaction = 1 + 1 = 2.
Rate = K [NO₃] [NO]

NO₃ is an intermediate which is formed rapidly by the collision of 1 molecule of NO and 1 molecule of O₂.

[NO₃] ∝ [NO][O₂]

Rate = K₁ [NO₃] [NO]

= K [NO] [O₂] [NO]
= K [NO]²[O₂]

Order of reaction is 2 + 1 = 3.