0.4g NaOH的物质的量= 0.4 / 40 = 0.01 mol NaOH + HCl = NaCl + H2O 0.01 x x = 0.01 mol 盐酸的物质的量浓度 = 0.01 ÷ (12.5×10^-3) = 0.8 mol/L
