Sodium Benzoate (NaC6H5CO2)
Sodium Benzoic Acid
pH = -log10(Ka) - log10([HA]/[A-])= 4.20 - log10([HA]/[A-])in which[HA] = 15.265(g) / 122.1(g.mol-1) / 500(mL) = 2.500*10-4 mol/mLand[A-] = 12.97(g) / 144.1(g.mol-1) / 500(mL) = 1.800*10-4 mol/mLSo pH = 4.20 - log10([2.5]/[1.8]) = 4.20 - log10(1.39) = 4.20 - 0.14 = 4.06