# A 0.200*g mass of sodium hydroxide is dissolved in a 0.500*L volume of water? What are pOH, and pH of this solution?

Jan 4, 2017

$p H = 14 - p O H$

#### Explanation:

$\left[H {O}^{-}\right] = \text{Moles of hydroxide"/"Volume of solution}$

$= \frac{\frac{0.2 \cdot g}{40.00 \cdot g \cdot m o {l}^{-} 1}}{0.500 \cdot L} = 0.01 \cdot m o l \cdot {L}^{-} 1$.

We (reasonably) assume no volume change on dissolution. Some heat will be evolved. Why?

$p O H = - {\log}_{10} \left[H {O}^{-}\right] = - {\log}_{10} \left({10}^{-} 2\right) = - \left(- 2\right) = 2$.

But we know for a fact that $p H + p O H = 14$

And thus pH=............?