1、HCOOH > HAc > HCN
HAc解离度 = [Ka/c(HAc)]^(1/2) = [1.76*10^(-5) * 0.1]^(1/2) = 1.33%
2、Kb = c(OH)^2/[c(NH3.H2O)-c(OH)]
= [1.34*10^(-3)]^2 / [0.1-1.34*10^(-3)]
= 1.80*10^(-5)
3、pH增加2,[H+]减少100倍,而[OH-]增加100倍；
pH减小3个单位,[H+]增大1000倍,而[OH-]减小1000倍
4、（1） pH = -lg0.2 = 0.7
(2) [OH-] = (1.8*10^(-5)*0.05)^(1/2) = 9.5*10^(-3)
pH = 14 + lg9.5*10^(-3) =11.02
(3) NaOH浓度不明,无法算.