Question

Calculate the ratio of $pH$ of a solution containing $1mole$ of $C{H}_{3}COONa+1mole$ of $HCl$ per litre and of other solution containing $1moleC{H}_{3}COONa+1mole$ of acetic acid per litre

• A. $1:1$
• B. $2:1$
• C. $1:2$
• D. $2:3$

Answer 1

Answer: (C)

$1:2$

For ${CH}_{3}COONa+HCl\to {CH}_{3}COOH+NaCl$

$\left[{CH}_{3}COOH\right]=1M$

$\left[H^{+}\right]=\sqrt{K_{a}C}=\sqrt{K_a}{pH}_1=-\frac{1}{2}log{K}_a$

Since it is a buffer,

${CH}_{3}COONa+{CH}_{3}COOH$

${PH}_2=-log{K}_a+log\frac{1}{1}=-log{K}_a$

$\frac{{pH}_1}{{pH}_2}=\frac{1}{2}$ Hence ratio is $1:2$