Question

Which of the following mixtures in aqueous solution of equimolar concentration acts as a buffer solution?

• A. $HN{O}_3+NaOH$
• B. $N{H}_{4}OH\left(excess\right)+HCl$
• C. $H_{2}S{O}_4+KOH$
• D. $C{H}_{3}COOH+NaOH\left(excess\right)$

Answer 1

Answer: (B)

A mixture of ammonium hydroxide and $HCl$ react to form ammonium chloride. This also contains unreacted ammonium hydroxide.

$N{H}_{4}OH+HCl\to N{H}_{4}Cl+H_{2}O$

Thus, the resulting mixture of $(N{H}_{4}OH+N{H}_{4}Cl)$ is a basic buffer solution. It contains a mixture of weak base ammonium hydroxide and its salt (ammonium chloride) with strong acid $\left(HCl\right)$.

It is used in a qualitative analysis of group $III$ radicals.

A mixture of $HN{O}_3$ and $NaOH$ is a mixture of strong acid and strong base similarly a mixture of $H_{2}S{O}_4$ and $KOH$ is also a mixture of strong acid and strong base, thus they do not form buffer solution.

Similarly, in option D mixture will form a strong base and salt of strong base weak acid hence it will not form a buffer solution.

Hence, option C is correct.