Ncert Exercises & Solutions

Arrange the following in increasing order of pH.

${KNO}_{3} (aq), {CH}_{3} COONa (aq), {NH}_{4} Cl (aq), C_{6} H_{5} {COONH}_{4} (aq)$

(i) KNO₃ is a salt of strong acid (HNO₃) strong base (KOH), hence its aqueous solution is neutral; pH=7.

(ii) CH₃COONa is a salt of weak acid (CH₃COOH) and strong base (NaOH), hence, its aqueous solution is basic; pH>7.

(iii) NH₄Cl is a salt of strong acid (HCl) and weak base (NH₄OH) hence, its aqueous solution is acidic; pH<7.

(iv) C₆H₅COONH₄ is a salt of weak acid, C₆H₅COOH and weak base, NH₄OH. But NH₄OH is slightly stronger than C₆H₅COOH. Hence, pH is slightly>7.

Therefore, increasing order of pH of the given salts is,

{NH}_{4} Cl < C_{6} H_{6} {COONH}_{4} < {KNO}_{3} < {CH}_{3} COONa