Dissociation Constants for Acids (HSC SSCE Chemistry): Flashcards

$K_a$

$K_a = \frac{[\text{H}_3\text{O}^+][\text{A}^-]}{[\text{HA}]}$

Solvent, concentration remains constant

Strong acids that ionise almost completely

Weak acids that only ionise to small extent

$K_a = \frac{[\text{H}_3\text{O}^+]^2}{[\text{HA}]}$

$\frac{[\text{H}_3\text{O}^+]}{[\text{HA}]_{\text{init}}} \times 100\%$

Acids that can donate more than one proton

$K_{a1} > K_{a2} > K_{a3}$ (first proton easiest to remove)

$\text{p}K_a = -\log_{10} K_a$