Sun May 01, 2011 By: Gaurav Avhad

H2SO4 gives 2 H+ ions but why the dissociation constant ka for the first H+ ions is high means why does H+ leave easily in first step can u explain me with the hybridisation and electron dot structure in animation?

Expert Reply
Mon May 02, 2011

In general, the rule is that successive pK values increase (Pauling's first rule). For example, for a diprotic acid, H2A (H2SO4), the two equilibria are

H2SO4 + H2O ? H3O+ + HSO4?    K1 = 2.4 x 106   (strong acid)
HSO4? + H2O ? H3O+ + SO42?     K2 = 1.0 x 10-2   

The second proton is removed from a negatively charged species. Since the proton carries a positive charge extra energy is needed to remove it.

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