Question

10.) What is the pH change when 19.4 mL of 0.119 M NaOH is added to 83.6 mL of a buffer solution consisting of 0.142 M NH3 and 0.191 M NH4Cl? (Ka for ammonium ion is 5.6x10^-10 .)

pH change =

Answer 1

Ans. Let          NH₃ = Weak base = B          ; NH₄⁺ = conjugate base = BH⁺

Given- Ka of conjugate acid NH₄⁺ = 5.6 x 10^-10

So, Kb of weak base NH₃ = 10^-14 / (5.6 x 10^-10) = 1.786 x 10^-5