課程名稱︰分析化學一 課程性質︰必帶 課程教師︰林萬寅 開課學院：理學院 開課系所︰化學系 考試日期（年月日）︰2010/11/08 考試時限（分鐘）：20(的樣子) 是否需發放獎勵金：是 （如未明確表示，則不予發放） Department: Name: Registered number: （←→表可逆符號） 1. Write the charge balance equation, mass balance equation and all chemical equibria for the saturated aqueous solution of Ca3(PO4)2. Neglect the hydrolysis of Ca2+ 20% ANS Charge balance: 2[Ca2+] + [H+] = [H2PO4–] + 2[HPO42–] + 3[PO43–] + [OH–] Mass balance: 2 [Ca2+] = 3([H3PO4] + [H2PO4–] + [HPO42–] + [PO43–]) Ca3(PO4)2(s) ←→ 3 Ca2+ +2 PO43- PO43- + H2O ←→ HPO42- + OH- HPO42- + H2O ←→ H2PO4- + OH- H2PO4- + H2O ←→ H3PO4 + OH- 2 H2O ←→ H3O+ OH- (or H2O←→H+ + OH-) 2. Find the pH of 1.0*10^-7 M HCl solution. ANS: Charge balance (or mass balance): [H+] = [OH-] + [Cl-] [Cl-] = 1.0*10-7M; activity coefficients ≒ 1 for H+ & OH- Kw =[H+][OH-]=([Cl-]+[OH-])[OH-]=1.0*10^-14 [OH-]=6.18*10^-8 M ; [H]=1.62*10^-7 M; pH=6.79 3. Find the solubility of Ag2CrO4(s) (Ksp=1.2*10^-12) in water with an ionic strength of 0.1M, knowing that the activity coefficients for Ag+ and CrO42- are 0.75 and 0.36, respectively. Neglect the hydrolysis of Ag+ and CrO42- ANS: 2 Ksp=[Ag+]^2[CrO4 2-](γAg+)*(γCrO4 2-) [CrO4 2-]=S ; [Ag+]=2S Ksp=4S^3*0.75*0.75*0.36=1.2*10^-12 S=1.1*10^-4M --

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