Question

What would be the pH of a buffer solution composed of equimolar amounts of C5H5NHCl and C5H5N ? The Kb of C5H5N is 1.7 x 10-4.

Answer 1

Answer – We are given the equimolar amounts of C₅H₅NHCl and C₅H₅N, means moles of conjugate acid and base are same, so both has same concentration and the ration of the conjugate acid by base is 1. We also know when conjugate acid and base has same concentration then pOH = pKb

We are given Kb = 1.7*10^-4

So, pKb = -log Kb

             = -log 1.7*10^-4

             = 3.77

So, pOH = 3.77

We know,

pH + pOH = 14

so, pH = 14 – pOH

            = 14-3.77

             = 10.23

So, pH of a buffer solution composed of equimolar amounts of C₅H₅NHCl and C₅H₅N is 10.23