Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Erik Hughes on 05/05/2010 09:30:03

Title: Is sulphuric acid stronger than sulphurous acid?
Post by: Erik Hughes on 05/05/2010 09:30:03

Erik Hughes  asked the Naked Scientists:
   
Hey Chris,

I've looked everywhere and I can't find a simple explanation to this problem.

Which acid is stronger, sulphuric acid (H2SO4) or sulphurous acid (H2SO3)?

I think its the Sulphuric acid but I'm not entirely sure.

Any help would be greatly appreciated.
Kind Regards,

Erik :D

What do you think?

Title: Is sulphuric acid stronger than sulphurous acid?
Post by: lightarrow on 05/05/2010 11:33:02

The answer is yes. H₂SO₄ is a very strong acid, it has an acidity constant much higher than 1 (it's very difficult to measure it in water because it's almost totally dissociated in its first dissociation) while H₂SO₃ is a weak acid, with acidity constant = 1.4*10^-2.

Just think that the associated base of H₂SO₄, that is the ion HSO₄^-, is practically as acid as H₂SO₃ (Ka = 1*10^-2)...