Ncert Exercises & Solutions

11. Which of the following will produce a buffer solution when mixed in equal volumes?

(1) $0.1 mol {dm}^{- 3} {NH}_{4} OH and 0.1 mol {dm}^{- 3} HCl$

(2) $0.05 mol {dm}^{- 3} {NH}_{4} OH and 0.1 mol {dm}^{- 3} HCl$

(3) $0.1 mol {dm}^{- 3} {NH}_{4} OH and 0.05 mol {dm}^{- 3} HCl$

(4) $0.1 mol {dm}^{- 3} {CH}_{3} COONa and 0.1 mol {dm}^{- 3} NaOH$

HINT-Weak base and its salt with strong acid forms buffer when both are present together in solution

EXPLAINATION(3) When the concentration of

{NH}_{4} OH

(weak base) is higher than the strong acid (HCl), a mixture of weak base and its conjugate acid is obtained, which acts as basic buffer

\underset{After reaction}{\underset{Initially}{_{}}} \underset{0.05 M}{\underset{0.1 M}{{NH}_{4} OH}} + \underset{0}{\underset{0.05 M}{HCl}} \to \underset{0.05 M}{\underset{0}{{NH}_{4} Cl}} + H_{2} O