The decomposition of hydrogen peroxide in the presence of iodide ion has been found to be first order in `H_2O_2`:
`2H_2O_2 (aq) overset(1^(-)(aq))(rarr) 2H_2O(l) + O_2 (g)`.
The rate constant has been found to be `1.01 xx10^(-2) " min"^(-1)` :
(a) Calculate the rate of reaction when `[H_2O_2] = 0.4" mol lit"^(-1)`.
(b) What concentration of `[H_2O_2]` would give a rate of `1.12 xx 10^(-2)" mol lit"^(-1)" min"^(-1)` ?

Explanation

`3H_2O_2(aq)I^(-)(aq)2H_2(l)+O_2(g)`
(a) As it is a first order reaction
Rate=`k[H_2O_2]`
`k=1.01xx10^(-2)" min"^(-1)`
`[H_2O_2]=0.4" mol L"^(-1)`
Rate=`1.01xx10^(-2)" min"^(-1)`
`xx0.4 " mol L"^(-1)`
`=4.04xx10^(-3)" mol L"^(-1)min^(-1)`
(b) Rate=`1.12xx10^(-2)" mol L^(-1)min^(-1)`
`[H_2O_2]=?`
`[H_2O_2]=("Rate")/(k)`
`=(1.12xx10^(-2)mol^(2)L^(-1)min^(-1))/(1.01xx10^(-2)" min"^(-2))`
`=1.11" mol L"^(-1)`