Two vessels X and Y contain aqueous solutions of a weak acid HA and its salt NaA , respectively. The following two equilibria HA + H ₂ O H ₃ O ⁺+ A ⁻ and A ⁻+ H ₂ O HA + OH ⁻ , exist in vessels X and Y , respectively. At equilibrium (at a given temperature T), the concentrations of HA , H ₃ O ⁺ and A ⁻ in vessel X are C ₁, C ₂ and C ₃ , respectively, while that of A ⁻, HA and OH ⁻ in vessel Y , are C ₄, C ₅ and C ₆ ,