Question

25℃,0.1 mol·L-1 NH3与0.1mol·L-1 NH4CL等体积混合后,溶液的[H]+和pH?

Answer 1

NH3·H2O=NH4++OH-

Kb=1.8*10^-5=[NH4+]*[OH-]/[NH3·H2O]=[0.05+X][OH-]/[0.05-X],因为X很小,为简便计算,0.05+X=0.05,0.05-X=0.05

1.8*10^-5=[0.05][OH-]/[0.05],[OH-]=1.8*10^-5,[H+]=10^-14/1.8*10^-5=5.6*10^-10,PH=9.25