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Question
Define order of reaction with suitable examples.
Solution
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,
aA + bB → cC + dD
If the rate of the reaction is given as
rate = k[A]x [B]y.
Then, the sum x + y gives overall order of the reaction.
e.g. For the reaction
H2(g) + I2(g) → 2HI(g) is
rate = k[H2][I2].
The reaction is of first-order in H2 and I2 each and hence overall order is second order.
For the reaction,
2H2O2(g) → 2H2O(l) + O2(g)
Experimentally determined rate law is rate = k[H2O2].
The reaction is of first-order in H2O2 and hence, the overall order is first order.
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