Question

$75ml$ of $0.2MHCl$ is mixed with $25ml$ of $1MHCl$. To this solution, $300ml$ of distilled water is added. What is the $pH$ of the resultant solution?

• A. $1$
• B. $2$
• C. $4$
• D. $0.2$

Answer 1

The correct option is A $1$

The concentration of the solution (n) $=\frac{numberofmoles}{totalvolume}=\frac{V_1{N}_1+V_2{N}_2}{totalvolume}$
Substitute values in the above expression,
$N=\frac{75\times 0.2+25\times 1}{400}=0.1N$
$pH=-log\left[H^{+}\right]=-log\left(0.1\right)=1$