Question

$0.05$ M ammonium hydroxide solution is dissolved in $0.001$M ammonium chloride solution. What will be the $O{H}^{-}$ ion concentration of this solution: $K_b\left(N{H}_{4}OH\right)=1.8\times {10}^{-5}$.

• A. $3.0\times {10}^{-3}$
• B. $9.0\times {10}^{-4}$
• C. $9.0\times {10}^{-3}$
• D. $3.0\times {10}^{-4}$

Answer 1

The correct option is B $9.0\times {10}^{-4}$

${\text{Given concentration NH}}_{4}OHC=0.05M$

$\begin{array}{c}N{H}_{4}Cl\rightleftharpoons {NH}_4+{Cl}^{-}\\ c00\\ c-xxx\end{array}$

$C=0.001M$

$\begin{array}{c}{K}_b=\frac{[N{H}_4+]\left[O{H}^{-}\right]}{\left[N{H}_{u}OH\right]}\\ \left[O{H}^{-}\right]=K_b\frac{\left[N{H}_{4}OH\right]}{\left[N{H}_4^{+}\right]}\end{array}$

$\begin{array}{cc}& =1.8\times {10}^{-5}\times \frac{0.05}{0.001}\\ \left[O{H}^{+}\right]& =9.0\times {10}^{-4}M\end{array}$