Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
A triprotic acid is an acid capable of donating three protons or hydrogen ions per molecule in aqueous solution. Examples include phosphoric acid ($H_3PO_4$) and citric acid.
5 Must Know Facts For Your Next Test
Triprotic acids undergo three distinct ionization steps, each with its own equilibrium constant ($K_a$).
The first ionization step typically has the highest $K_a$ value, indicating it is the strongest of the three acidic protons.
In a triprotic acid, the subsequent ionizations occur less readily, with each $K_a$ value decreasing sequentially.
The pH of a solution containing a triprotic acid can be calculated by considering all three ionization equilibria.
Polyprotic acids like triprotic acids are important in biological systems and industrial processes for their buffering capacity.
Review Questions
Related terms
Diprotic Acid: An acid that can donate two protons or hydrogen ions per molecule in aqueous solution.
$K_a$ (Acid Dissociation Constant): A quantitative measure of the strength of an acid in solution; specifically, it measures how completely an acid dissociates into its ions.
$pH$: A scale used to specify how acidic or basic an aqueous solution is. It is logarithmically related to the concentration of hydrogen ions in a solution.