# Why exactly is sulphuric acid a good dehydrating agent?

I have seen in many organic reactions (such as esterificatiton) that sulphuric acid is added both as a catalyst and a dehydrating agent. What I don't get is exactly how this strong acid is able to dehydrate the solution full of water.

One explanation I've heard is that the acid protonates the water forming $$\ce{H3O+}$$ which thus "removes" the water. Is this the "dehydrating" process? In the esterification equilibrium system, would the protonation of water count as "removing" water and shift the equilibrium?

• H20 has spare electron pairs which means it can act as a nucleophile. Protonation removes this nucleophilic ability so H2O cannot participate in the reverse reaction. – Waylander Apr 10 at 8:29