Answer to Question #309214 in General Chemistry for Kaikai

Question

The pkas of two monoprotic acods HA and HB are 5.9 and 8.1 respectively. Which of the two is the stronger acid?

Answer 1

pK_a(HA) = 5.9; K_a(HA) = 10^-5.9;

pK_a(HB) = 8.1; K_a(HB) = 10^-8.1;

Therefore, the higher value pK_a correspond the lower value K_a and the lower value pK_a correspond the higher value K_a.

K_a = [H⁺] * [A^-] / [HA]

[H⁺] =K_a * [HA] / [A^-]

Therefore, the higher value K_a correspond the stronger acid.

So, HA is the stronger acid with the value pK_a 5.9.

Answer: HA.