Question

Equal volumes of two $HCl$ solutions of $pH=3$ and $pH=5$ were mixed. What is the $pH$ of the resulting solution?

• A. $3.5$
• B. $4.0$
• C. $4.5$
• D. $3.3$

Answer 1

Answer: (D)

$3.3$

$pH=-log\left[H_3{O}^{+}\right]$
$H_1^{+}={10}^{-3}$ and $H_2^{+}={10}^{-5}$
Total concentration of $H^{+}=\frac{{10}^{-3}+{10}^{-5}}{2}=\frac{101\times {10}^{-5}}{2}$
So, $pH=3.3$