设碳酸钠浓度为a mol/L 已知pKb = 3.67pH = 9.8时，[OH^-] = 10^-4.2CO3^2- + H2O = HCO3^- + OH^- a-10^-4.2 10^-4.2 10^-4.2[OH^-][HCO3^- ]/[CO3^2-] = 10^-3.67a = 8.17e-5mol/L
