## Chemistry: Principles and Practice (3rd Edition)

$[OH^-] = 2.5 \times 10^{- 7}M$
1. Use "$K_w$" to calculate the $[OH^-]$ $[H_3O^+] * [OH^-] = Kw = 10^{-14}$ $4 \times 10^{- 8} * [OH^-] = 10^{-14}$ $[OH^-] = \frac{10^{-14}}{ 4 \times 10^{- 8}}$ $[OH^-] = 2.5 \times 10^{- 7}M$