Part A.Answer all eight questions(5 marks each). 1.Why is Ka2<Ka for a diprotic acid such as H2SO? In the second hydrolysis,a proton is being removed from a doubly charged SO4 ion,which requires more energy than the first hydrolysis,where a proton is being removed from only a singly charged HSOion. 2.A reaction has AH<0and AS0.Is this reaction spontaneous at high temperature,low temperature,both or neither? △G=△H°_T△S.Since△S<0,this reaction will be spontaneous at low temperature.At higher temperature, the-T△S°term will become sufficiently positive that△G°will become positive. 3.A solution is made by dissolving I mole of KClis)in I mole H2O.What is the mole fraction of H2O in this solution? The KCls dissociates into two ions.Thus,the water will be only 1/3 of the particles in solution,and thus its mole fraction will be 0.333. 5.A galvanic cell has the shorthand notation Pb(s)Pb)1 MI Pb)2 M Pbs).Is the cell potential positive or negative? The oxidation reaction is Pb(s)>Pb(ag)(1 M)+2 e.The reduction is Pb()(2 M)+2 e Pb(s).The overall reaction is therefore Pb(2 M)Pb(1 M).For this reaction,Q==0.5.According to the Nernst cquation,EER().Since Q1 In(Q)and so E>E,But since 0 nF 7.Melting ice is an endothermic process.Why is it spontaneous? Because the process has a positive entropy change. 8.For the reaction H2O=HO initially at equilibrium,which direction will the equilibrium shift (left or right)if the pressure is increased? 1 Part A. Answer all eight questions (5 marks each). 1. Why is Ka2 < Ka1 for a diprotic acid such as H2SO4(aq)? In the second hydrolysis, a proton is being removed from a doubly charged SO4 -2 ion, which requires more energy than the first hydrolysis, where a proton is being removed from only a singly charged HSO4 - ion. 2. A reaction has ΔH0 <0 and ΔS0 <0. Is this reaction spontaneous at high temperature, low temperature, both or neither? ΔGo = ΔHo –TΔSo . Since ΔS < 0, this reaction will be spontaneous at low temperature. At higher temperature, the –TΔSo term will become sufficiently positive that ΔGo will become positive. 3. A solution is made by dissolving 1 mole of KCl(s) in 1 mole H2O(l). What is the mole fraction of H2O(l) in this solution? The KCl(s) dissociates into two ions. Thus, the water will be only 1/3 of the particles in solution, and thus its mole fraction will be 0.333. 5. A galvanic cell has the shorthand notation Pb(s) | Pb+2 (aq), 1 M || Pb+2 (aq), 2 M | Pb(s). Is the cell potential positive or negative? The oxidation reaction is Pb(s) → Pb+2 (aq) (1 M) + 2 e¯. The reduction is Pb+2 (aq) (2 M) + 2 e¯ → Pb(s). The overall reaction is therefore Pb+2 (aq) (2 M) → Pb+2 (aq) (1 M). For this reaction, Q = ½ = 0.5. According to the Nernst equation, o RT E E ln(Q) nF = − . Since Q<1, ln(Q) < 0, and so E > Eo , But since Eo = 0, E > 0 7. Melting ice is an endothermic process. Why is it spontaneous? Because the process has a positive entropy change. 8. For the reaction H2O(l) = H2O(g) initially at equilibrium, which direction will the equilibrium shift (left or right) if the pressure is increased? 1