CH3COONa已知浓度、电离平衡常数求pH,水解度

设：水解平衡时的[OH-]为y (mol/L)
Ac- + H2O = HAc + OH-
平衡时：c-y y y
K = [HAc] × [OH-] ÷[Ac-]
= ([HAc] × [OH-] × [H+] )÷ ([Ac-] × [H+])
= Kw ÷ Ka
K= Kw ÷ Ka = 1.0*10^-14 ÷ 1.8*10^-5 = 5.56*10^-10
∵[HAc] × [OH-] ÷[Ac-] = y^2 / ( c-y) = K (∵ (c-y) ≈ c )
∴ y = √ ( c × K)
= √ (0.1*5.56*10^-10) = 7.45*10^-6 (mol/L)
POH= -Lg(7.45*10^-6)=5.13
因此：PH = 14 - 5.13 = 8.87
水解度=y ÷ c*100% = 7.45*10^-6 ÷0.1 × 100% = 0.00745%