Question

The $H^{+}$ion concentration of a solution is $4\times {10}^{-5}M$. Then the ${OH}^{-}$ ion concentration of the same solution is:

• A. $4\times {10}^{-5}M$
• B. $2.5\times {10}^{-9}M$
• C. $1.0\times {10}^{-7}M$
• D. $2.5\times {10}^{-10}M$

Answer 1

Answer: (D)

$2.5\times {10}^{-10}M$

For any solution,

$\left[H^{+}\right]\left[O{H}^{-}\right]={10}^{-14}$

$\Rightarrow 4\times {10}^{-5}\times \left[O{H}^{-}\right]={10}^{-14}$

$\Rightarrow \left[O{H}^{-}\right]=2.5\times {10}^{-10}M$

Hence $D$ is the correct answer