In solutions of H2SO4 in water, the econd dissociation constant Ka2, is less than first dissociation constant Ka1. why?

This is due to the fact that acids have tendencies to lose the first proton easily but tend not to lose the second proton in solution very easily.

Sulfuric acid loses one proton to form negatively charged HSO4- ion which is a weaker acid as compared to sulfuric acid and therefore the second dissociation constant is less than the first dissociation constant.

H2SO4(aq) + H2O(l) ----> H3O+(aq) + HSO4-(aq)  Ka1 = 1 x 103
HSO4-(aq) + H2O(l) <---->H3O+(aq) + SO42-(aq)  Ka2 = 1.2 x 10-2

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it shows acidic character

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When H2SO4 gives out its first H+, it is neutral, after which is converts into HSO4-.

Since HSO4- is negatively charged, it shows less tendency to give out another H+ ( due to attraction between positive H+ and negative HSO4-)

And since KA represents the strength of the acid or indirectly the tendency of the acid to give out H+ ion, KA of the 1st reaction is more than that of the second reaction.

Hope that helped! :)

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