Practical investigations
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I am reacting magnesium with different strength acids and finding the activation energy of each reaction. Why does the strength of an acid effect the activation energy of a reaction?
I can see why it would effect the rate but not the activation energy.
Ulex replies
If you assume that the metal-acid reaction involves only the H+(aq) ions, you would expect the activation energy for a reaction involving a weak acid to be a few kJ less than that for a strong acid, because some energy has to be expended in ionising the weak acid. There are two problems with this argument. One is that these ‘few kJ’ may only be 5 kJ or so, and it is difficult to work to that degree of accuracy in this sort of measurement. The other is that there is some evidence that the hydrogen atom of the undissociated acid also reacts with magnesium!
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updated: 16 March 2006
