Question

Name one salt whose solution has pH less than 7 and one salt with pH more than 7.

Answer 1

Acidic salt solutions:

1. The salt solution which has strong acid and weak bases is acidic in nature. They have a pH of less than 7.
2. They have weak bases such as Ammonium hydroxide$\left({\mathrm{NH}}_4\mathrm{OH}\right)$ and strong acids such as Sulphuric acid$\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ and Hydrochloric acid$\left(\mathrm{HCl}\right)$

${\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{aq}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\stackrel{}{\to }{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, a salt whose solution with a pH of less than 7 is Ammonium chloride$\left({\mathrm{NH}}_4\mathrm{Cl}\right)$.

Basic salt solutions:

1. The salt solution which has strong bases and weak acid is basic in nature. They have a pH of more than 7.
2. They have strong bases such as Sodium hydroxide$\left(\mathrm{NaOH}\right)$ and Potassium hydroxide$\left(\mathrm{KOH}\right)$, and weak acids such as Carbonic acid$\left({\mathrm{H}}_2{\mathrm{CO}}_3\right)$ and Phosphoric acid$\left({\mathrm{H}}_3{\mathrm{PO}}_4\right)$.

$2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)\stackrel{}{\to }{\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, a salt with a pH of more than 7 is Sodium carbonate$\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$.