Question

You make up a solution of a diprotic acid, H2A, having pKa values of 5.0 and 9.0. Identify the primary, secondary, and tertiary species when you set the pH equal to 8.0 by addition of KOH.

Answer 1

Step-by-step explanation:

A solution with a pH value of 7 is neutral i.e neither acidic nor alkaline. A solution with a pH less than 7 is said to be acidic, while one with a pH value more than 7 is alkaline. Acidity increases as the value decrease below 7, while alkalinity increases as the value increase about 7.

Given that H2A is a diprotic weak acid have pKa values of 5.0 ad 9.0, it will undergo dissociation in the solution as:

NOTE: These reactions are reversible reactions.

`\mathbf{H_2A \to H^+ + HA^- \ \ \ pKa = 5.0}`

`\mathbf{HA^- \to H^+ +A^(2-) \ \ \ pKa = 9.0}`

Thus;

The primary species is HA⁻

The secondary species is A²⁻