pKa (AQA A-Level Chemistry): Flashcards

Logarithmic measure of acid strength derived from $K_a$

$pK_a = -\log_{10} K_a$

$K_a = 10^{-pK_a}$

$[\text{HA}]_{\text{initial}} \approx [\text{HA}]_{\text{equilibrium}}$

$[\text{H}^+] = \sqrt{K_a \times [\text{HA}]_{\text{initial}}}$

$pH = -\log_{10}[\text{H}^+]$

$pH = pK_a$

$[\text{HA}]$ and $[\text{A}^-]$ concentrations equal

$4.74$

Express small $K_a$ values manageably