Explanation:
When a strong acid, say [tex]HCl[/tex] reacts which a weak base, say [tex]NH_3[/tex], the reaction is shown below as:-
[tex]\text{NH}_3 (\text{aq}) + \text{HCl} (\text{aq}) \rightarrow {\text{NH}_4^+}(\text{aq}) + \text{Cl}^-(\text{aq})[/tex]
The salt further reacts with water as shown below:-
[tex]\text{NH}_4^+ + \text{H}_2\text{O} \rightarrow \text{H}_3\text{O}^+ + \text{NH}_3[/tex]
Formation of [tex]\text{H}_3\text{O}^+[/tex] lowers the pH value of the solution as more hydrogen ions leads to less pH.
