Create assignment, 48975, Exam 2, Apr 05 at 9:07 am 1This print-out should have 30 questions.Multiple-choice questions may continue onthe next column or page – find all choicesbefore making your selection. The due time isCentral time.PLEASE remember to bubble in yourname, student ID number, and version num-ber on the scantron!Msci 17 063117:06, general, multiple choice, > 1 min, fixed.001Which of the following equilibria is unaffectedby a pressure change?1. 2 NaCl(s)*)2 Na(s) + Cl2(g)2. H2(g) + I2(g)*)2 HI(g) correct3. 2 NO2(g)*)N2O4(g)4. O2(g)*)2 O(g)Explanation:Equilibria is unaffected by pressure changeswhen the number of moles of gas on the prod-uct side is equal to the number of moles of gason the reactant side.Msci 17 061517:06, general, multiple choice, > 1 min, fixed.002Suppose we let the exothermic reaction2 SO2(g) + O2(g)*)2 SO3(g)come to equilibrium. Then we decrease thetemperature of the reaction mixture, whileholding the volume constant.What will be the effect on the net amountof SO3(g) present?1. It increases. correct2. It decreases.3. It does not change.4. The question cannot be answered withoutknowledge of the numerical value of KcorKp.5. The question cannot be answered withoutknowledge of the numerical value of ∆H.Explanation:An exothermic reaction gives off heat and sodecreasing temperature will favor the forwardreaction, increasing [SO3] .Holt da 18 1 practice 117:02, highSchool, numeric, < 1 min, wording-variable.003At equilibrium a mixture of N2, H2, NH3gasat 500◦C is determined to consist of 0.602mol/L of N2, 0.420 mol/L of H2, and 0.113mol/L of NH3.What is the equilibrium constant for thereactionN2(g) + 3 H2(g)*)2 NH3(g)at this temperature?Correct answer: 0.286294 .Explanation:[N2] = 0.602 mol/L [NH3] = 0.113 mol/L[H2] = 0.42 mol/L K = ?N2(g) + 3 H2(g)*)2 NH3(g)K =[NH3]2[N2][H2]3=(0.113 mol/L)2(0.602 mol/L) (0.42 mol/L)3= 0.286294Msci 17 0210x17:02, general, multiple choice, < 1 min, fixed.004Consider the reactionA+2 B*)C + 2 DThis reaction has an equilibrium constantof 3.7 × 10−3. Consider a reaction mixturewith[A] = 2.0 × 10−2M[B] = 1.7 × 10−4M[C] = 2.4 × 10−6M[D] = 3.5 × 10−3MCreate assignment, 48975, Exam 2, Apr 05 at 9:07 am 2Which of the following statements is defi-nitely true?1. The forward reaction can occur to agreater extent than the reverse reaction untilequilibrium is established.2. The system is at equilibrium.3. The reverse reaction can occur to agreater extent than the forward reaction untilequilibrium is established. correct4. Heat will be evolved.5. No conclusions about the system can bemade without additional information.Explanation:Q =[C] [D]2[A] [B]2=(2.4 × 10−6) (0.0035)2(0.02) (0.00017)2= 0.0508651 > KTherefore the reaction will shift back to theleft (reverse).Msci 17 0510 nowarning17:05, general, multiple choice, < 1 min, nor-mal.005For the reactionPOCl3(g)*)POCl(g) + Cl2(g)Kc= 0.30. An initial 0.3 moles of POCl3areplaced in a 3 L container with initial concen-trations of POCl and Cl2equal to zero.What is the final concentration of POCl3?1. final concentration = 0.079 M2. final concentration = 0.021 M correct3. final concentration = 0.185 M4. final concentration = 0.285 M5. final concentration = 0.042 MExplanation:[POCl3]initial=0.3 mol3 L= 0.1 MPOCl3(g)*)POCl(g)+ Cl2(g)ini, M 0.1 − −∆, M −x x xeq, M 0.1 − x x xKc=[Cl2] [POCl][POCl3]=x20.1 − x= 0.3x2= 0.03 − 0.3xx2+ 0.3 x − 0.03 = 0x =−0.3 ±p(0.3)2− 4 (1) (−0.03)2 (1)= 0.079 or − 0.38[POCl3] = 0.1 − x = 0.021 MMsci 17 020717:10, general, multiple choice, > 1 min, fixed.006Given the reversible reaction equation2 CO(g) + O2(g)*)2 CO2(g)which is the relationship between Kcand Kp?1. Kp= Kc(R T )22. Kp= KcR T3. Kp= Kc4. Kp= Kc(R T )−1correct5. Kp= Kc(R T )−2Explanation:The ideal gas law can be used to derive thelink between Kcand Kp:P =nVR T = M R TM =PR TCreate assignment, 48975, Exam 2, Apr 05 at 9:07 am 3Kc=[CO2]2[CO]2[O2]=P2CO2(R T )2P2CO(R T )2·PO2R T=P2CO2P2CO· PO2R T= KpR TorKp= Kc(R T )−1Msci 17 110017:12, general, multiple choice, > 1 min, .007What is ∆G for the reactionN2O4(g) +12O2(g) → N2O5(g)if each gas is present at a partial pressure of0.1 atm and 25◦C?1. 20.03 kJ/mol correct2. 16.52 kJ/mol3. 17.46 kJ/mol4. 17.61 kJ/mol5. 17.4 kJ/mol6. 16.53 kJ/mol7. None of theseExplanation:Q =(PN2O5)(PN2O4)(PO2)1/2=(0.1)(0.1)√0.1= 3.16228∆G0= ∆G0f(N2)5(g)) − ∆G0f(N2O4(g))−12∆G0f(O2)= 115 kJ/mol − 97.82 kJ/mol − 0= 17.18 kJ/mol∆G = ∆G0+ R T ln K= 17.18 kJ/mol+µ8.314 Jmol · K¶(298.15 K) ln(3.16228)·1 kJ1000 J= 20.0338 kJ/molMsci 18 031318:03, general, multiple choice, > 1 min, fixed.008At 100◦C, the ionization constant of water isKw= 1.0 × 10−13.What is the pH of pure water at 100◦C?1. 1.02. 6.5 correct3. 7.04. 7.55. 13.0Explanation:2 H2O*)H3O++ OH−Kw= [H3O+][OH−] = 1.0 × 10−13In pure water,[H3O] = [OH−] =p1.0 × 10−13M= 3.16228 × 10−7MpH = −log 3.16228 × 10−7= 6.5Mlib 66 006718:03, basic, multiple choice, > 1 min, fixed.009The solution which has the highest pH is theone withCreate assignment, 48975, Exam 2, Apr 05 at 9:07 am 41. 5 × 10−2mol HCl in 1.0 L of solution.2. 5 ×10−2mol H2SO4in 0.5 L of solution.3. 5 ×10−2mol NaOH in 1.0 L of solution.4. 5×10−2mol Ba(OH)2in 0.5 L of solution.correct5. All of these have the same pH.Explanation:The basic solutions NaOH and Ba(OH)2will have pH above 7. The other solutions areacidic and will have pH lower than 7. BothNaOH and Ba(OH)2are strong bases whichcompletely dissociate to give OH−ions.NaOH −→ Na++ OH−[OH−] =5 × 10−2mol1 L soln= 5 × 10−2MBa(OH)2−→ Ba2++ 2 OH−[OH−] =2 (5 × 10−2) mol0.5 L soln= 20 MMsci 19 500718:03, general, multiple choice, > 1 min, fixed.010What is the concentration of OH−ions in a0.40 M solution of KCN?The ionization constant of HCN is 4.0 ×10−10.1. 1.60 × 10−102. 1.26 × 10−53. 6.25 × 10−54. 3.16 × 10−3correct5. 4.08 × 10−12Explanation:Msci 18 041818:04, general, multiple choice, > 1 min, fixed.011Given the following hypothetical acids, withpKavalues:AcidHP−HQH2RH4Z+H2XpKa1.9210.337.219.2511.62Which of these is the strongest acid?1. HP correct2. HQ3. H2R4. H4Z5. H2XExplanation:Mlib 76 146018:99, basic, multiple choice, > 1 min, fixed.012Hard water deposits (calcium carbonate) havebuilt up around your bathroom sink.Which one of the following would be bestto dissolve the deposit?1. vinegar correct2. ammonia3. bleach4. lyeExplanation:Msci 18 072019:02,
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