Question

Four grams of $NaOH$ solid are dissolved in just enough water to make $1$ litre of solution. What is the$\left[H^{+}\right]$ of the solution?

• A. ${10}^{-2}$ moles/litre
• B. ${10}^{-1}$ moles/litre
• C. ${10}^{-12}$ moles/litre
• D. ${10}^{-13}$ moles/litre

Answer 1

Answer: (D)

${10}^{-13}$ moles/litre

Moles of $NaOH=\frac{4}{40}=0.1$

$NaOH$ dissolves into water, thus dissociating into its respective ions as

$NaOH(aq.)\rightleftharpoons N{a}^{+}(aq.)+C{l}^{-}(aq.)$

Hence, $\left[O{H}^{-}\right]=\frac{0.1}{1}=0.1moles/litre$

Since, $\left[H^{+}\right]\left[O{H}^{-}\right]={10}^{-14}moles/litre$

Therefore, $\left[H^{+}\right]={10}^{-13}moles/litre$