Question

Arrange in order of decreasing acidity. Strongest to weakest. And explain how you did this

Answer 1

The order is B>C>A>E>D

Explanation: The acid strength depends on the stability of conjugate base. Also, lower the pKa of the acid greater the acidity.

HI is the strongest inorganic acid because it has pKa of -9.95 and the corresponding anion i.e I- is very stable.

Then benzene sulphonic acid is the stronger one because of the three electronegative oxygen atoms pulling electron density from the O-H bond. Also the conjugate base i.e SO₃^- is very stable because of resonance.

benzoic acid comes to the next where the conjugate base less stable than C but more stable than the conjugate base of E.

At last, D is the weakest acid due to it's strong O-H bond and lack of stability to the conjugate alkoxide anion.