What is the protonated form of HA at equilibrium?

2020-04-14 12:26 pm
If HA is a weak acid, is the protonated form or de-protonated form of the acid the major form of HA at equilibrium?

回答 (2)

2020-04-14 12:49 pm
The term "protonated form" is misused here. Protonation means addition of proton (H⁺), and thus the protonated form of HA is H₂A⁺. This happens when a weak acid is protonated by a concentrated strong acid. For example, acetic acid CH₃COOH is protonated in concentrated sulfuric acid, and the protonated form is CH₃COOH₂⁺.

Consider the ionization of weak acid HA: HA(aq) ⇌ H⁺(aq) + A⁻(aq)
We often refer HA as acid molecule, and refer A⁻ as anion or the conjugate base of HA.
In the above equilibrium, the major form of the weak acid is HA molecule.
2020-04-14 12:30 pm
When the question asks about the protonated or unprotonated form,

HA is the protonated form, and A- is the unprotonated form in the equilibrium:HA <--> H+ + A-

In a solution of HA, because it is a weak acid, most of the molecules are in the protonated form HA.


收錄日期: 2021-04-30 17:39:53
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