Question

Why is it that when you have a strong acid and weak base your equivalence point is less than 7

Answer 1

Explanation:

When a strong acid, say $HCl$ reacts which a weak base, say $NH_3$, the reaction is shown below as:-

$\text{NH}_3 (\text{aq}) + \text{HCl} (\text{aq}) \rightarrow {\text{NH}_4^+}(\text{aq}) + \text{Cl}^-(\text{aq})$

The salt further reacts with water as shown below:-

$\text{NH}_4^+ + \text{H}_2\text{O} \rightarrow \text{H}_3\text{O}^+ + \text{NH}_3$

Formation of $\text{H}_3\text{O}^+$ lowers the pH value of the solution as more hydrogen ions leads to less pH.