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My teacher told me that on changing temperature of a reaction, its activation energy ($E_{a}$) and pre-exponenetial factor ($A$) do not change significantly and hence we can assume them to be constant on changing the temperature. But my question is why? Why don't they change significantly? Even in the graph given in my textbook (given below), on changing temperature they have assumed activation energy to be constant. Is it really true? Please clarify. Would greatly appreciate it! Graph between fraction of molecules and kinetic energy of the gas molecules of a gas sample

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    $\begingroup$ The activation energy is determined by the electronic interactions between the reactants as they collide and form a transition state, and not on temperature. The pre-exponential terms does depend on temperature but the effect is generally small, it mainly depends on how many times the reactants collide per second. $\endgroup$
    – porphyrin
    Apr 24 at 6:51
  • $\begingroup$ On what factors does the activation energy depend on? Could you please tell me? $\endgroup$ Apr 24 at 10:28
  • $\begingroup$ This may help. $\endgroup$
    – Rishi
    Apr 24 at 14:02
  • $\begingroup$ As I write in my comment, it depends on the electronic properties of the molecules involved, ie. the energy of the transition state complex which is sort of half reactants and half product. Calculating the energy of this is very hard particularly as there is little or no experimental data. If the reaction is AX+B $\to$ A-X-B $\to$ A+BX it is the energy of A-X-B. $\endgroup$
    – porphyrin
    Apr 24 at 15:52

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