Question

$pH$ of an aqueous solution is $5.5$. The hydroxyl ion concentration in the solution would be

• A. $-5.5M$
• B. $-8.5M$
• C. ${10}^{-8.5}M$
• D. ${10}^{8.5}M$

Answer 1

The correct option is C

${10}^{-8.5}\mathrm{M}$

Explanation of correct option:

• $pH$ of an aqueous solution$=5.5$
• $\left[H^{+}\right]$ ion concentration$={10}^{-pH}$
• $\left[H^{+}\right]={10}^{-5.5}$
• We know that, $\left[H^{+}\right]\left[O{H}^{-}\right]={10}^{-14}----\left(1\right)$
• Substituting the value of $\left[H^{+}\right]$ in equation $\left(1\right)$ we get,
• ${10}^{-5.5}\times \left[O{H}^{-}\right]={10}^{-14}$
• $\left[O{H}^{-}\right]={10}^{-8.5}M$

Hence option C is correct.