溶液中有HA的电离平衡和水的电离平衡.
NaA === Na+ + A-
HA =可逆= H+ + A- Ka == [H+] [A-] / [HA] [HA] ==0.1 mol/L
H2O =可逆= H+ + OH- Kw == [H+] [OH-]
[A-] == Ka [HA] / [H+]
[OH-] == Kw / [H+]
[A-] / [OH-] == Ka [HA] /Kw
因为Ka是10 的负3---12 次方,Kw 是10的负14 次方,所以[A-] 》[OH-] .
0.0004 mol/L CaCl2溶液中,Ca++ 0.0004mol/L ,Cl- 0.0008mol/L .