Question

Which one of the following mixture is considered as an acidic buffer solution ?

• A. $HCN+NaCN$
• B. $HCN+N{H}_{4}CN$
• C. $HCl+NaCl$
• D. $C{H}_{3}COOH+HCOOK$

Answer 1

The correct option is A $HCN+NaCN$

Mixture of weak acid and salt of the weak acid and strong base will make a acidic buffer solution.

• $HCN$ is a weak acid. $NaCN$ is a salt of $HCN$(weak acid) and $NaOH$ (strong base). So the resultant solution is called a buffer solution.
• Although $HCN$ is a weak acid but the salt $N{H}_{4}CN$ is a salt of weak base ($N{H}_{4}OH$) and weak acid ($HCN$). Therefore the mixture is not a acidic buffer.
• $HCl$ is a strong acid and $NaCl$ is a salt of strong acid ($HCl$) and strong base ($NaOH$). So it is not a buffer solution.
• $C{H}_{3}COOH$ is a weak acid . But $HCOOK$ is a mixture of weak acid ($HCOOH$) and strong base ($KOH$). Therefore it is not a buffer solution.