MCQ
The ionization constant of a certain weak acid is ${4}$. What should be the [salt] to [acid] ratio if we have to prepare a buffer with $ pH = 5$ using this acid and one of the salts
- A$1:10$
- ✓$10:1$
- C$5:4$
- D$4:5$
✓
Answer
Correct option: B.
$10:1$
(b) $pH = - \log {K_b} + \log \frac{{[{\rm{salt}}]}}{{{\rm{[acid]}}}}$
$5 = - \log {10^{ - 4}} + \log \frac{{[{\rm{salt}}]}}{{{\rm{[acid]}}}}$
$\log \frac{{[{\rm{salt}}]}}{{{\rm{[acid]}}}} = 1$
$\frac{{[{\rm{salt}}]}}{{{\rm{[acid]}}}} = {\rm{antilog}}\,1 = 10:1$
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