Question

Meanings of Ka and pKa (a) Does a strong acid have a greater or lesser tendency to lose its proton than a weak acid? (b) Does the strong acid have a higher or lower Ka than the weak acid? (c) Does the strong acid have a higher or lower pKa than the weak acid?

Answer 1

Answer:

(a) A strong acid has a greater tendency to lose its protons.

(b) A strong acid has a higher Ka than a weak acid.

(c) A strong acid has a lower pKa than a weak acid.

Explanation:

A strong acid has the ability to completely transfer their protons to the water, making a complete dissociation. Instead, a weak acid only dissociates partially, how much it dissociates depends on the acid dissociation constant (Ka).

The weak acids always are in equilibrium, and the equilibrium depends on the acid dissociation constant.

$HA + H_{2}O$ ⇄ $A^{-} + H_{3}O^{+}$

Thus, a stronger acid with a bigger Ka produces more dissociation and a higher concentration of protons.

The equation that defines pKa is:

$pKa = -Log (Ka)$

Therefore, a higher pKa means a lower Ka and also a weaker acid.