NCERT Class XI Chemistry Equilibrium Solutions

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Question : 51
Total: 73
The pH of 0.005 M codeine (C18H21NO3) solution is 9.95. Calculate its ionization constant and pKb.
Solution:  
[H+] = antilog (- 9.95) = 1.12 × 10−10
∴ [OH−] =
1.0×10−14
1.12×10−10
= 8.92 × 10−5 M
But Kb =
[M+][OH−]
[MOH]
=
(8.92×10−5)2
0.005
= 1.59 × 10−6
pKb = - log Kb = - log (1.59 × 10−6) = 5.80
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