Question

The $pH$ of a solution obtained by mixing $50mL$ of $0.2MHCl$ with $50mL$ of $0.02M$ ${CH}_{3}COOH$ is:

• A. $0.30$
• B. $0.70$
• C. $1.00$
• D. $2.00$

Answer 1

The correct option is C $1.00$

First we need to find the number of moles used

$n\left(HCl\right)=0.2\times \frac{50}{1000}=0.01$ mol

$n\left({CH}_{3}COOH\right)=0.2\times \frac{50}{1000}=0.01$ mol

$n\left(HCl\right):n\left({CH}_{3}COOH\right)$

$1:1$

$HCl+{CH}_{3}COOH⟶H_{2}O+{CH}_{3}COOCl$

So, $0.01$ mol of $HCl$ remain $=\frac{0.01}{\frac{100}{1000}}=0.1mol/{dm}^3$

$pH=-log\left[H^{+}\right]=-log\left[0.1\right]$

$\Rightarrow pH=1$