Which among the following pair constitute a buffer?
Which among the following pair constitute a buffer?
$\mathrm{LiOH}$ and $\mathrm{LiCl}$
$\mathrm{HNO}_3$ and $\mathrm{NH}_4 \mathrm{NO}_3$
$\mathrm{HNO}_2$ and $\mathrm{NaNO}_2$
$\mathrm{HBr}$ and $\mathrm{KBr}$
Solution
Buffer solution consists of mixture of weak acids and their salts or weak base and their salts. $\mathrm{LiOH}$ is a strong base whereas $\mathrm{HNO}_3$ and $\mathrm{HBr}$ are strong acids.
$\mathrm{HNO}_2$ is a weak acid and $\mathrm{NaNO}_2$ is a salt formed by combination of weak acid $\left(\mathrm{HNO}_2\right)$ and strong base $(\mathrm{NaOH})$.
Buffer $=\mathrm{HNO}_2+\mathrm{NaNO}_2$.