Write the differential rate expression for the following reaction and determine its order of reaction:
$H_{2}O_{2} + I^{-} \rightarrow H_{2}O + IO^{-}$
$H_{2}O_{2} + IO^{-} \rightarrow H_{2}O + I^{-} + O_{2}$

(N/A) The overall reaction is the sum of the two elementary steps: $2H_{2}O_{2} \rightarrow 2H_{2}O + O_{2}$.
The rate of the reaction is determined by the slow step,which is the first step: $H_{2}O_{2} + I^{-} \rightarrow H_{2}O + IO^{-}$.
The differential rate expression is given by: $Rate = -\frac{d[H_{2}O_{2}]}{dt} = k[H_{2}O_{2}][I^{-}]$.
The order of the reaction is the sum of the powers of the concentration terms in the rate law: $1 + 1 = 2$. Thus,the reaction is of second order.