Answer
$[OH^-] = 7.14 \times 10^{- 12}M$
Work Step by Step
1. Since HCl is a strong acid:
$[HCl] = [H_3O^+]$
2. Calculate $[H_3O^+]$ using $[OH^-]$:
$[H_3O^+] * [OH^-] = Kw = 10^{-14}$
$ 1.4 \times 10^{- 3} * [OH^-] = 10^{-14}$
$[OH^-] = \frac{10^{-14}}{ 1.4 \times 10^{- 3}}$
$[OH^-] = 7.14 \times 10^{- 12}$
