Question

Which of the following aqueous solutions are good buffer systems?
.

0.30 M nitric acid + 0.23 M potassium nitrate

0.21 M acetic acid + 0.16 M potassium acetate

0.14 M calcium hydroxide + 0.24 M calcium chloride

0.30 M ammonia + 0.35 M barium hydroxide

0.31 M sodium chloride + 0.21 M potassium chloride

B.)

Which of the following aqueous solutions are good buffer systems?
.

0.22 M hydrochloric acid + 0.16 M sodium chloride.

0.12 M hydrocyanic acid + 0.11 M perchloric acid.

0.30 M ammonia + 0.37 M ammonium bromide.

0.34 M calcium chloride + 0.28 M potassium chloride.

0.18 M potassium hydroxide + 0.26 M potassium bromide.

Answer 1

Buffer solution is a mixture of weak acid and it's conjugate base or it is also defined as weak base and it's conjugate acid. The main advantage of buffer solution is to maintain a constant pH in a solution.

1)

In the given set of options the correct option is second one. i.e 0.21 M acetic acid+ 0.16 M potassium acetate.

This is best for in the given set because the given acid is weak acid and its conjugate base potassium acetate. It is a weak electrolyte, it should not change pH much. when we add acid it will react with potassium acetate and we add base it will neutralize with acid.

2)

In the given set of options the correct option is third one. i.e 0.30 M ammonia+0.37 M ammonium bromide.

if we add hydroxide then ammonia will form ammonium hydroxide which is a weak electrolyte and pH will not change much. Further ammonium bromide is added to decrease the dissociation of ammonium hydroxide. So, pH will not change.