State the method of preparation of ethanol:

(a) by hydrolysis of ethene.

(b) by hydrolysis of ethyl bromide.

(a) Hydrolysis of ethene — Ethanol is produced when ethene is heated with water at 300°C and 60 atmosphere pressure in presence of phosphoric acid (catalyst).

$\underset{\text{ ethene}}{\text{C}$2\text{H}4} + \text{H}2\text{O} \xrightarrow[300\degree\text{C, 60 atm.}]{\text{H}3\text{PO}4} \underset{\text{ethanol}}{\text{C}2\text{H}_5\text{OH}}

(b) Hydrolysis of ethyl bromide — Ethanol can be prepared by boiling aq. NaOH with ethyl bromide.

$\underset{\text{ Bromoethane [ethyl bromide]}}{\text{C}$2\text{H}5\text{-Br}} + \underset{\text{ aqueous}}{\text{NaOH}} \xrightarrow{\text{boil}} \underset{ \text{ethanol}} {\text{C}2\text{H}5\text{OH}} + \text{NaBr}