Question Bank [2022] — Chemistry STD 12 Science — Question
Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryQuestion Bank [2022]2 Marks
Question
Define order of reaction with suitable examples.
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Answer
The order or overall order of the chemical reaction is given as the sum of powers of the concentration terms in the rate law expression.
For the reaction,
$a A+b B \rightarrow c C+d D$
If the rate of the reaction is given as
$\text { rate }=k[A]^{x}[B]^{y}$
Then, the sum $x+y$ gives overall order of the reaction.
e.g. For the reaction
$H _{2(g)}+ I _{2(g)} \rightarrow 2 HI _{( g )}$ is
$\text { rate }=k\left[H_2\right]\left[I_2\right]$
The reaction is of first-order in $H _2$ and $I _2$ each and hence overall order is second order.
For the reaction,
$2 H_2 O_{2(g)} \rightarrow 2 H_2 O_{(l)}+O_{2(g)}$
Experimentally determined rate law is rate $=k\left[ H _2 O _2\right]$.
The reaction is of first-order in $H 2 O 2$ and hence, the overall order is first order.
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