[nata_li]

My book does not mention anything about catalytic hydration, but I see it several times on my supplementary exercise.

Its solution says ethene can be turned into ethanol by catalytic hydration. Can anyone help by telling me what is the catalyst required? I only know something about fermentation.

[english]

A strong acid, usually sulfuric acid, H₂SO₄.

"Catalytic hydration" is just a fancy way of saying that ethene is reacting with water, with an acid catalyst.

The acid converts H₂O to H₃O⁺:  H₂SO₄ + H₂O <----> H₃O⁺ + HSO₄^-.  This is what actually reacts with ethene.  The hydrogen bonds in water are too strong to break without the catalyst.

Protonating water increases its acidity, thereby making it more reactive.