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Explain the effect of increase of temperature on rate of reaction and rate constant. |
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Answer» Solution :Most of the chemical reactions are ACCELERATED by increase in temperature. E.g. :In decompositon of `N_(2)O_(5)` the time taken for half of the original amount of material is as under:  E.g.2:in a mmixture of `KMnO_(4)` and `H_(2)C_(2)O_(4)` potassium premagnate gets decolourused faster at a high temperature than that at a LOWER temperature . It has been foud that for a chemical reation witgh rise in temperature by `10^(@)` C the rateconstant isnearly doubled. As the temperature increase by `10^(@)` the graph of fraction of molecules `(N_(E))/(N_(T))` kinetic energyshift towards right side and fraction of molecules becomes double. The temperature dependence of the rate of a chemical reaction can be accurately explained byArrhenius equation . `k=Ae^(-E_(a))/(RT)` ...(i) k=ratem constant =Rate Where A=arrhenius factor or the FREQUECY factor.It is also CALLED pre-exponential reaction 0R=gas contant =`8.214 JK^(-1) "mol"^(1)` `E_(a)` =activation energy 1 `mol^(-1)` Taking netural logarithm of both side of eq,(i) In k=`-(E_(a))/(RT)+`in A and log k=`-(E_(a))/(2.303RT)`+log A `:. In k prop 1/T` Increase in temperature then increase in the rate of the reaction and an exponential increase in the rate constant. So, temperature is less then rate is less and temperature increase then rate increase. |
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