∴ [H+] = 0.1 M pH = – log [H+] = – log 0.1 = 1 (ii) NaCl is a salt of strong acid and strong baseso it is not hydrolysed and hence its pH is 7. (iii) NH4Cl + H2O ⇌ NaOH + HCN ∴ The solution is acidic and its pH is less thanthat of 0.1 M HCl. (iv) NaCN + H2O ⇌ NaOH + HCN ∴ The solution is basic and its pH is more thanthat of 0.1 M HCl. ∴ Correct order for increase in pH is HCl < NH4Cl < NaCl < NaCN