JEE Main Chemistry question
A buffer solution is prepared in which the concentration of NH₃ is 0.30 M and NH₄⁺ is 0.20 M. If the equilibrium constant, Kb for NH₃ equals 1.8×10⁻⁵ what is the pH of this solution? (log 2.7 = 0.43)
Answer: (C)
Solution
pOH=pKb+log([NH₄⁺]/[NH₃])=4.745+log(2/3)=4.745−0.176=4.57; pH=14−4.57=9.43.