C5H5N dissociates as:
C5H5N +H2O -----> C5H5NH+ + OH-
0.1 0 0
0.1-x x x
Kb = [C5H5NH+][OH-]/[C5H5N]
Kb = x*x/(c-x)
Assuming x can be ignored as compared to c
So, above expression becomes
Kb = x*x/(c)
so, x = sqrt (Kb*c)
x = sqrt ((1.7*10^-9)*0.1) = 1.304*10^-5
since c is much greater than x, our assumption is correct
so, x = 1.304*10^-5 M
So, [OH-] = x = 1.304*10^-5 M
% C5H5NH+ = [C5H5NH+]*100 / initial [C5H5N]
= x*100 / 0.1
= (1.304*10^-5)*100/0.1
= 0.013 %
Answer: A
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