A 0.20 mol/L solution of propionic acid has a pH of 2.79. What is the #"p"K_text(a)# of propionic acid?
First, calculate the equilibrium concentration of H₃O⁺.
pH = 2.79
Second, write the balanced chemical equation and set up an ICE table.
HA +H₂O ⇌ A⁻ + H₃O⁺
I/mol·L⁻¹: 0.20; 0; 0
E/mol·L⁻¹: 0.20 -
We know that at equilibrium, [H₃O⁺] = [A⁻] =
and [HA] = (0.20 -