设稀释前 NH3*H2O的浓度为 X
NH3 + H2O NH4+ + OH-
Kb=1.75x10^-5=[OH-]^2/X
[OH-]^2=1.75x10^-5X
pOH=-log[OH-]= -0.5(log1.75x10^-5 + logX)
=2.37-0.5logX
那么,稀释后 NH3*H2O的浓度为 X/2
pOH'=2.37-0.5log(X/2)=2.52-0.5logX
pOH'-pOH=2.52-2.37=0.15
所以,溶液的pH 将降低 0.15个 pH 单位