A student is asked to determine the acid dissociation constant, Kₐ, for butanoic acid, CH3CH2CH2COOH. Kₐ = [CH3CH2CH2COO⁻][H⁺] / [CH3CH2CH2COOH] The student is told to measure the pH of eight buffer solutions containing CH3CH2CH2COOH and the salt sodium butanoate, CH3CH2CH2COO⁻Na⁺. The salt provides butanoate ions, CH3CH2CH2COO⁻, as the base. Each buffer solution contains a different ratio of [CH3CH2CH2COOH] to [CH3CH2CH2COO⁻]. Each buffer solution is prepared by mixing different volumes of distilled water, 2.00 mol dm⁻³ CH3CH2CH2COOH and 2.00 mol dm⁻³ CH3CH2CH2COO⁻Na⁺.