NCERT Class XI Chemistry Equilibrium Solutions

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Question : 62
Total: 73
A 0.02 M solution of pyridinium hydrochloride has pH = 3.44. Calculate the ionization constant of pyridine.
Solution:  
Pyridinium hydrochloride is a salt of weak base and strong acid.
Therefore, pH = 7 −
1
2
(log X + pKb)
where Kb = dissociation constant of pyridine
3.44 = 7 -
1
2
(log 0.02 + pKb)
- 3.56 =
1
2
(1.70+pKb)
⇒ - 7.12 = 1.0 - pKb
pKb = 1.70 + 7.12 = 8.82,
Kb = antilog (– 8.82) = 1.513 × 109
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