[高中] 計算溶解度

[wercell (wercell)]

請板上高手為我解惑
CH3COOAg之Ksp=3.6*10^-3
CH3COOH之Ka=1.8*10^-5
求CH3COOAg在pH=5溶液中的溶解度?

我的算法是
CH3COO- + H+ → CH3COOH.........  1/Ka
CH3COOAg → CH3COO- + Ag+.......  Ksp
------------------------------------------
CH3COOAg + H+ → CH3COOH + Ag+... K=(3.6*10^-3)/(1.8*10^-5)
                                   =200
         10^-5 M   X M     X M

X^2/(10^-5)=200
X=4.47*10^-2 M...........即為溶解度

但解答為7.5*10^-2 M
請告訴我是哪裡出錯了~感激不盡~


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