Question

The pH of 0.1 M solution of the following compounds increases in the order:

• A. $NaCl<N{H}_{4}Cl<NaCN<HCl$
• B. $HCl<N{H}_{4}Cl<NaCl<NaCN$
• C. $NaCN<N{H}_{4}Cl<NaCl<HCl$
• D. $HCl<NaCl<NaCN<N{H}_{4}Cl$

Answer 1

The correct option is B $HCl<N{H}_{4}Cl<NaCl<NaCN$

$NaCN$ is a salt of a strong base and weak acid, has the highest pH. $HCl$ is a strong acid and has the lowest pH. $NaCl$ is a neutral salt - strong base and strong acid mix to give this and has a pH of 7. $N{H}_{4}Cl$ is a salt of a strong acid and a weak base, has a pH less than 7.
$\therefore pH:HCl<N{H}_{4}Cl<NaCl<NaCN$