The mechanism of the reaction, 2 H 2 + 2 NO ⟶ N 2 + 2 H 2 O follows these | TestHub

Passage / Comprehension

The order of reaction is an experimentally determined quantity. It may be zero, positive, negative, or fractional. The kinetic equation for an nᵗʰ-order reaction is:

$k \times t = \frac{1}{( n - 1 )} [\frac{1}{( a - x ) ^{n - 1}} - \frac{1}{a ^{n - 1}}]$

The half-life of an nᵗʰ-order reaction depends on the initial concentration according to the following relation:

$t_{1/2} \propto \frac{1}{a ^{n - 1}}$ .

The unit of the rate constant varies with the order, but the general relation for the unit of an nᵗʰ-order reaction is:

$U ni t o f k = [\frac{1}{( co n c . )}]^{n - 1} . (T im e)^{- 1}$

The differential rate law for an nᵗʰ-order reaction may be given as:

$\frac{d x}{d t} = k [A]^{n}$

where A denotes the reactant.

The mechanism of the reaction,

$2 H_{2} + 2 NO ⟶ N_{2} + 2 H_{2} O$

follows these steps:

$2 NO ⇌ N_{2} O_{2}$

$N_{2} O_{2} + H_{2} ⟶ N_{2} O + H_{2} O (s l o w)$

$N_{2} O + H_{2} ⟶ N_{2} + H_{2} O (f a s t)$

The overall order of the reaction is:

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Answer:

Solution:

The overall order is determined by the slow step:

rate = $k [N_{2} O_{2}] [H_{2}]$ .

From the first step, $[N_{2} O_{2}] = K [NO]^{2}$ .

Substituting gives rate = $k K [NO]^{2} [H_{2}]$ .

Thus, the overall order is $2 + 1 = 3$ .

Chemistry - Chemical Kinetics Question with Solution | TestHub

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