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Question
Define order of reaction with suitable examples.
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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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