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188.8.131.52.134.0.7correctExplanation:122 g Sr(OH)2×1 mol122 g= 1 mol Sr(OH)21 mol Sr(OH)210 L H2O= 0.1 M Sr(OH)2Sr(OH)2(aq)↔Sr2+(aq) + 2 OH−(aq)[OH−] = Cb·2 = 0.1M·2 = 0.2MpOH =-log[OH−] =-log(0.2) = 0.70236.0 pointsThevaporpressureofpureacetone(CH3COCH3) at 30oC is 240 torr.If salt(NaCl) is dissolved into a sample of acetoneuntil the total vapor pressure of the mixtureat 30oC is 180 torr, what is the mol fractionof acetone?184.108.40.206.75correct220.127.116.11.8Explanation:P = Poacetone·χacetoneχacetone=PPoacetoneχacetone=180240= 0.750246.0 pointsWhich of the following is a possible combina-tion of values for ΔHlattice, ΔHhydrationandΔHsolution, respectively, for a salt whose dis-solution is endothermic.1.+640,-620,and + 20 kJ·mol−1,cor-rect2.-900,-900,and-1800 kJ·mol−1,3.-450,+400,and-50 kJ·mol−1,4.+550,-480,and + 1030 kJ·mol−1,Explanation:ΔHsolution= ΔHlattice+ ΔHhydration- theproblem stipulates that ΔHsolutionbe positive(endothermic) and this limits the values theother two terms can have.0256.0 pointsWhat would be the pH of a 0.25 M solutionof phenylamine (C6H5NH2) at room temper-ature? The Kbof phenylamine is 4×10−10.1.10.52.18.104.22.168correctExplanation:[OH−] = (Kb·Cb)1/2= (4×10−10·0.25)1/2= (10−10)1/2= 10−5pOH =-log[OH−] =-log(10−5) = 5pH = pKw-pOH = 14-5 = 90266.0 pointsAccording to the given phase diagram forcarbon dioxide, what are regions 1, 3 and Brespectively?Carbon Dioxide
Version 295 – Exam 1 – Laude – (52390)83142AB200250300350400100101102103104Pressure, barTemperature, K1.solid, liquid, triple point2.solid, vapor, critical pointcorrect3.liquid, vapor, critical point4.solid, liquid, critical point5.solid, vapor, triple pointExplanation:As temperature goes up, gas forms. As tem-perature decreases, solid forms.As pressureincreases, solid forms. As pressure decreases,gas forms.Point A is the triple point, andPoint B is the critical point.1 = solid, 2 =liquid, 3 = vapor, 4 = supercritical region0276.0 pointsNitric oxide, NO, is a toxic chemical pro-duced in automobile engines.O2(g) + N2(g)←→2 NO(g)At 2100◦C,K= 0.0031 and at 25◦C,K= 2.5×10−32. ΔH of this reaction is (pos-itive/negative) and it would be best to runan engine as (hot/cold) as possible to reduceemissions of NO.1.positive, coldcorrect2.negative, hot3.positive, hot4.negative, coldExplanation:The direct proportionality between temper-ature andKdemonstrates that ΔH is positiveand to prevent the reaction, the engine shouldbe run as cold as possible.0286.0 pointsAn unknown liquid has a vapor pressure of88 mmHg at 45◦C and 39 mmHg at 25◦C.What is its heat of vaporization?1.2000 kJ/mol2.2000 J/mol3.32000 kJ/mol4.32 kJ/molcorrectExplanation:UsetheClausius-ClapeyronEquation.Here, the only thing we don’t know is ΔHvap.ln(P2P1) =ΔHvapR(1T1-1T2)ΔHvap=Rln(P2/P1)1/T1-1/T2ΔHvap= 32.0 kJ/mol0296.0 pointsWhich of the following statements regard-ing colligative properties is/are true?I) Pure liquid water exhibits a lower freez-ing point than a solution of magnesiumchloride in water.