Answer
$[OH^-] = 4 \times 10^{-5}$;
It's a basic solution.
Work Step by Step
1. Knowing that [H+] * [OH-] = $10^{-14}$; Find [OH-]:
$[H^+] \times [OH^-] = 10^{-14}$
$2.5 \times 10^{-10} \times [OH^-] = 10^{-14} $
$[OH^-] = \frac{10^{-14}}{2.5 \times 10^{-10}} $
$[OH^-] = 4 \times 10^{-5}$
2. Because $[OH^-] > [H^+]$, the solution is considered basic.
