Question

A buffer of acetic acid $(p{K}_a=4.8)$ with sodium acetate will be, when ${CH}_{3}COOH$ and ${CH}_{3}COONa$ are present in equivalent amounts has pH limits equal to:

• A. $0$ to $4.8$
• B. $3.8$ to $5.8$
• C. $4.3$ to $5.3$
• D. $4.8$

Answer 1

Answer: (B)

$3.8$ to $5.8$

$pH$ of buffer of acetic acid and sodium acetate can be represented as :

$pH={pK}_a+log\frac{\left[{CH}_{3}COONa\right]}{\left[{CH}_{3}COOH\right]}$

$=4.8+log\frac{\left[{CH}_{3}COONa\right]}{\left[{CH}_{3}COOH\right]}$

$=4.8\pm 1$ (if $\frac{\left[{CH}_{3}COONa\right]}{\left[{CH}_{3}COOH\right]}=0.1$ or $10$)

$pH$ limits equal to $3.8$ to $5.8$.