Equilibrium Question 508

Question: The ionization constant of a certain weak acid is $ {10^{-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 [CPMT 2000; KCET 2000; Pb. CET 2000]

Options:

A) $ 1:10 $

B) $ 10:1 $

C) $ 5:4 $

D) $ 4:5 $

Show Answer

Answer:

Correct Answer: B

Solution:

$ pH=-\log K_{b}+\log \frac{[salt]}{[\text{ acid }]} $

$ 5=-\log {10^{-4}}+\log \frac{[salt]}{[\text{ acid }]} $

$ \log \frac{[salt]}{[\text{ acid }]}=1 $

$ \frac{[salt]}{[\text{ acid }]}=antilog,1=10:1 $



NCERT Chapter Video Solution

Dual Pane