Question

Equal volumes of two solutions having pH $=1$ and pH $=4$ are mixed together. The pH of the resulting solution is:

• A. $1.301$
• B. $3.010$
• C. $4.699$
• D. $3.699$

Answer 1

Answer: (A)

$1.301$

It is given that equal volumes of two solutions having $pH=1$ and $pH=4$ are mixed together.

The values of pH equal to $1$ and $4$ correspond to hydrogen ion concentrations of ${10}^{-1}M$ and ${10}^{-4}M$ respectively.

Assume $x$ L of each solution is mixed.

The concentration of resulting solution is given by $\frac{0.1\times x+0.0001\times x}{x+x}=\frac{0.1+0.0001}{2}=0.05M$

$pH=-log\left[H^{+}\right]=-log\left(0.05\right)=1.3010$

Hence, the pH of the resulting solution is $1.3010$.