Give reasons for the following :
(t) Ethyl iodide undergoes `SN_(2)` reaction faster than ethyl bromide.
(ii) `(pm)` 2-Butanol is optically inactive.
(iii) C- X bond length in halobenzene is smaller than C-X bond length in `CH_(3) -X`.

Explanation

(i) Ethyl iodide `I^(-)` ion is better leaving group than `Br^(-)` ion, therefore, ethyl iodide reacts faster than ethyl bromide in `S_(N)2` reaction with `OH^(-)` ion.