Answer:
A reaction between a strong acid and a weak base.
Step-by-step explanation:
The conjugate acid of a weak base is a strong acid.
![\underbrace{\hbox{H}_(3)\text{O}^(+)}_{\hbox{acid}} + \underbrace{\hbox{B}}_{\hbox{base}} =\underbrace{\hbox{BH}^(+)}_{\hbox{acid}} + \underbrace{\hbox{H}_(2)\text{O}}_{\hbox{acid}}](https://img.qammunity.org/2019/formulas/chemistry/high-school/ed2j70qjzpd4me5dw0s2g9gwi5ckcapice.png)
The reaction above is reversible, so we can write
![\underbrace{\hbox{BH}^(+)}_{\hbox{acid}} + \underbrace{\hbox{H}_(2)\text{O}}_{\hbox{base}}\rightleftharpoons \underbrace{\hbox{H}_(3)\text{O}^(+)}_{\hbox{acid}} + \underbrace{\hbox{B}}_{\hbox{base}}](https://img.qammunity.org/2019/formulas/chemistry/high-school/hdlrjcwff6ed1t2gqyz2o1c7exrxwjae1o.png)
Thus, the solution of the salt will be acidic, because it produces hydronium ions.
Example;
Ammonium chloride is the salt of a strong acid (HCl) and a weak base (NH₃).
Solutions of NH₄Cl are acidic.