Question

In a $2.4\times {10}^{-3}M$ Hydrogen bromide ($HBr$) solution, find the concentration of $O{H}^{-}$ ?

• A. $2.17\times {10}^{-12}$
• B. $1.17\times {10}^{-12}$
• C. $6.17\times {10}^{-12}$
• D. $4.17\times {10}^{-12}$

Answer 1

The correct option is D $4.17\times {10}^{-12}$

The dissociation of water equation is used to find $\left[O{H}^{-}\right]$.
$K_w=\left[H_3{O}^{+}\right]\left[O{H}^{-}\right]=1.0\times {10}^{-14}$.
Solve for $\left[O{H}^{-}\right]$
$\left[O{H}^{-}\right]=\frac{(1.0\times {10}^{-14})}{\left[H_3{O}^{+}\right]}$
Hydrogen bromide (HBr) is a strong acid. So it will completely dissociate in its aqueous solution. The dissociation reaction is given below :
$HBr+H_{2}O\to H_3{O}^{+}+B{r}^{-}$
Using molarity of $HBr$, solve for $O{H}^{-}$
$\left[O{H}^{-}\right]=\frac{(1.0\times {10}^{-14})}{[2.4\times {10}^{-3}]}=4.17\times {10}^{-12}$