Question

The sum of $pH$ and $p{K}_b$ for a basic buffer solution is 13. The ratio of the concentration of the base to that of the salt is

• A. 10
• B. 1
• C. 0.05
• D. 0.1
• E. 20

Answer 1

Answer: (D)

From $pOH=p{K}_b-\log \frac{[\text{ base }]}{[\text{ salt }]}$

$14-pH=p{K}_b-\log \frac{[base]}{[salt]}$

$\therefore 14=pH+p{K}_b-\log \frac{[\text{ base }]}{[\text{ salt }]}$

or $14=13-\log \frac{[\text{ base }]}{[salt]}$

$\log \frac{[\text{ base }]}{[\text{ salt }]}=13-14=-1$

$\therefore \frac{[\text{ base }]}{[\text{ salt }]}=$ antilog $(-1)=0.1$