HA in the graph represents a weak acid.
Explanation
Is HA an acid or a base?
Apply the Arrhenius Theory of Acids and Bases.
- Acids ionize in water to produce [tex]\text{H}^{+}[/tex] (or equivalently [tex]\text{H}_3\text{O}^{+}[/tex]) and a conjugate ion.
- Bases ionize in water to produce [tex]\text{OH}^{-}[/tex] and a conjugate ion.
The equation in the picture shows that HA ionizes in water to produce [tex]\text{H}_3\text{O}^{+}[/tex] ions. By the Arrhenius Theory of acids and bases, HA is an acid.
Is HA a weak acid or a strong acid?
Both weak and strong Arrhenius acids ionize in water to produce [tex]\text{H}^{+}[/tex] (or equivalently [tex]\text{H}_3\text{O}^{+}[/tex]) and a conjugate ion. However,
- Strong acids ionize completely. There would be nearly no acid left in the solution. Expect arrows [tex]\to[/tex] ⇒ in only one direction in the equation.
- Weak acids also ionize, but only partially. There would be plenty of acid left in the solution. Expect two-sided arrows like ⇔ and two-sided harpoons like [tex]\rightleftharpoons[/tex] in the equation.
As seen in the bar chart, there are plenty of HA left after ionization. HA ionizes only partially. Also, the equation shows a two-sided arrow. As a result, HA is a weak acid.
