Question

Calculate the pH of an aqueous ammonia solution that has an OH-concentration of 3.9 × 103M. Is the solution more basic or acidic

Answer 1

Solution.

$\begin{bmatrix} OH^- \\ \end{bmatrix}=3.9\sdot 10^3M;$

$\begin{bmatrix} H^+ \\ \end{bmatrix}\begin{bmatrix} OH^- \\ \end{bmatrix}=1\sdot10^{-14}\implies \begin{bmatrix} H^+ \\ \end{bmatrix}=\dfrac{1\sdot10^{-14}}{\begin{bmatrix} OH^- \\ \end{bmatrix}};$

$\begin{bmatrix} H^+ \\ \end{bmatrix}=\dfrac{1\sdot10^{-14}}{ 3.9\sdot10^3 }=2.56\sdot10^{-18};$

$pH=-log\begin{bmatrix} H^+ \\ \end{bmatrix}$ ;

$pH=-log(2.56\sdot10^{-18})=17.59;$

The solution is basic.

Answer: $pH=17.59,$  the solution is basic.