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Explain the rate determining step with an example. |
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Answer» Solution :(i) Let us consider reaction, the decomposition of hydrogen peroxide catalysed by `I^(-)`. `2H_(2)O_(2(aq))rarr 2H_(2)O_((l))+O_(2(g))` (II)It is experimentally FOUND that the reaction is first order with respect to both `H_(2)O_(2)` and `I^(-)`, which indicates that `I^(-)` is also involved in the reaction. The MECHANISM involves the following steps. Step : 1 `H_(2)O_(2(aq))+I_((aq))^(-)rarr H_(2)O_((l))+OI_((aq))^(-)` Step : 2 `H_(2)O_(2(aq))+OI_((aq))^(-)rarr H_(2)O_((l))+I_((aq))^(-)+O_(2(g))` Overall reaction is `2H_(2)O_(2(aq))rarr 2H_(2)O_((l))+O_(2(g))` (iii) Thesetwo reactions are elementary reactions. Adding equ (1) and (2) gives the overall reaction. Step 1 is the rate determining step, since it involves both `H_(2)O_(2)` and `I^(-)`, the overall reaction is bimolecular. |
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