Question

Calculate the pH of a solution which is 0.1 M in HA and 0.5 M in NaA. Ka for HA is 1.8 × 10^-6 ?

Answer 1

HA + H₂O ⇌ H₃O⁺ + A⁻

NaA → Na⁺ + A^-

pH = pK_a + log\(\frac{[Salt]}{[acid]}\)

= − log (1∙8 × 10⁻⁶) + log \(\frac{[0.5]}{[0.1]}\)

= 5∙744 + 0∙6990

= 6∙44.