Calculate the pH of an aqueous ammonia solution that has an OH-concentration of 3.9 × 103M. Is the solution more basic or acidic
Solution.
[OH−]=3.9⋅103M;\begin{bmatrix} OH^- \\ \end{bmatrix}=3.9\sdot 10^3M;[OH−]=3.9⋅103M;
[H+][OH−]=1⋅10−14 ⟹ [H+]=1⋅10−14[OH−];\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}};[H+][OH−]=1⋅10−14⟹[H+]=[OH−]1⋅10−14;
[H+]=1⋅10−143.9⋅103=2.56⋅10−18;\begin{bmatrix} H^+ \\ \end{bmatrix}=\dfrac{1\sdot10^{-14}}{ 3.9\sdot10^3 }=2.56\sdot10^{-18};[H+]=3.9⋅1031⋅10−14=2.56⋅10−18;
pH=−log[H+]pH=-log\begin{bmatrix} H^+ \\ \end{bmatrix}pH=−log[H+] ;
pH=−log(2.56⋅10−18)=17.59;pH=-log(2.56\sdot10^{-18})=17.59;pH=−log(2.56⋅10−18)=17.59;
The solution is basic.
Answer: pH=17.59,pH=17.59,pH=17.59, the solution is basic.
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