Chemistry Exam 2020

Note: For all questionsinvolving solutionsand/or chemical equations,assumethat the systemis in pure water and at G temperatureunlessotherwisestated. Part A Directions: Each set of letteredchoicesbelow refers to the numberedquestionsor statementsimmediately following it. Select the one letteredchoice that bestanswerseach questionor bestfits each statementand then fill in the correspondingoval on the answersheet.A choice may be used once, more than once, or not at all in each set. Questions5-7 refer to the phasediagrambelow of a pure substance. Questionsl-4 (4 Heisenberguncertaintyprinciple (B) Pauli exclusionprinciple K> Hund’s rule (principle of maximum multiplicity) 0) Shieldingeffect 03 Wave nature of matter P 1. Can be usedto predict that a gaseouscarbon atom in its groundstateis paramagnetic (atm) 2. Explains the experimentalphenomenonof electron diffraction ’ lb ’ io ’ ’ do ’ iio’ i30- T (“Q 3. Indicatesthat an atomic orbital can hold no more than two electrons (A) (B) (C) (D) (E) 4. Predictsthat it is impossibleto determinesimultaneouslythe exact positionand the exact velocity of an electron Sublimation Condensation Solvation Fusion Freezing 5. If the temperatureincreasesfrom 10” C to 60” C at a constantpressureof 0.4 atmosphere,which of the processesoccurs? 6. If the temperaturedecreasesfrom 110” C to 40” C at a constantpressureof 1.1 atmospheres,which of the processesoccurs? 7. If the pressureincreasesfrom 0.5 to 1.5 atmospheres at a constanttemperatureof 50” C, which of the processesoccurs? q 11a Questions8-10 refer to the following diatomic species. (A) (B) (C) 0) (E) Liz I% N 02 FZ Questions11-13 (4 Pb (W Ca cc>zn 0% As (E) Na 8. Has the largestbond-dissociation energy 11. Utilized as a coating to protect Fe from corrosion 9. Has a bond order of 2 12. Is addedto silicon to enhanceits propertiesas a semiconductor 10. Contains1 sigma(CT)and 2 pi (7~)bonds 13. Utilized as a shieldfrom sourcesof radiation Part B Directions: Each of the questionsor incompletestatementsbelow is followed by five suggestedanswersor completions. Select the one that is bestin each caseand then fill in the correspondingoval on the answersheet. 14. Which of the following is lower for a l.O-molar aqueoussolutionof anysolutethan it is for pure water? (A) PH (B) (C) (D) (E) Vapor pressure Freezing point Electrical conductivity Absorptionof visible light 15 In a moleculein which the central atom exhibits sp3d2 hybrid orbitals,the electronpairs are directed 16. Commercial vinegar was titrated with NaOH solutionto determinethe contentof acetic acid, HC2H302. For 20.0 milliliters of the vinegar, 26.7 milliliters of 0.600-molar NaOH solutionwas required.What was the concentrationof acetic acid in the vinegar if no other acid was present? (A) (B) (C) (D) (E) 1.60 A4 0.800 M 0.600 M 0.450 A4 0.200 M towardthe cornersof (A) (B) (C) (D) (E) a tetrahedron a square-based pyramid a trigonal bipyramid a square an octahedron 17. Relatively slow ratesof chemical reactionare associated with which of the following? (A) (B) (C) (D) (E) The presenceof a catalyst High temperature High concentrationof reactants Strong bondsin reactantmolecules Low activationenergy 18. 2 HZ0 + 4 Mn04- + 3 C102- + 4 MnOz + 3 ClOh- + 4 OHWhich speciesactsas an oxidizing agentin the reactionrepresented above? (A) (B) (C) (D) (E) Hz0 ClodClOzMn02 Mn04- 19. In which of the following compoundsis the massratio of chromium to oxygen closestto 1.62 to 1.00 ? (A) (B) (C) (D) (E) 20. Cr-03 CrOr CrO Cr,O CrzO, . . . Ag’ + . . . ASH,(~) + . . . OH- + . . . Ag(s) + . . . H3As03(aq) + . . . Hz0 When the equationaboveis balancedwith lowestwhole-numbercoefficients,the coefficient for OH- is (A) (B) (C) (D) (E) 2 4 5 6 7 2 1. Correct statementsaboutalpha particlesinclude which of the following? I. They havea massnumberof 4 and a charge of +2. II. They are more penetratingthan beta particles. III. They are helium nuclei. (A) (B) (C) (D) (E) I only III only I and II I and III II and III HSO,- + HZ0 =+ H30+ + SO:- 22. In the equilibrium representedabove,the species that act as basesinclude which of the following? I. HS04 II. HZ0 III. sod2(A) (B) (C) (D) (E) II only III only I and II I and III II and III Step 1: Ce4++ Mn2++ Ce3++ Mn3+ 23. Step 2: Ce4++ Mn3++ Ce3++ Mn4+ Step 3: Mn4++ Tl’ + T13++ Mn2+ The proposedstepsfor a catalyzedreaction betweenCe4+and Tl’ are representedabove.The productsof the overall catalyzedreactionare (A) (B) (C) (D) (E) Ce4+and Tl’ Ce3+and T13+ Ce3+and Mn3+ Ce3+and Mn4+ T13+and Mn2’ 24. A sampleof 0.0100 mole of oxygen gasis confined at 37” C and 0.216 atmosphere.What would be the pressureof this sampleat 15” C and the same volume? (A) (B) (C) (D) (E) 0.0876 atm 0.175 atm 0.201 atm 0.233 atm 0.533 atm 25. Hz(g) + $ Wg) + HzO@) AH” = -286 kJ 2 Na(s) + i O?(g) + NalO(s) AH” = -414 kJ Na(s)+$Ol(g)+~H~(g)+NaOH(s) AH”=-425kJ Basedon the informationabove,what is the standardenthalpy changefor the following reaction? NazO(s) + H,O(!?) + 2 NaOH(s) (A) -1,125 kJ (B) -978 kJ (C) -722 kJ (D) -150 kJ (E) +275 kJ 26. Which of the following actionswould be likely to changethe boiling point of a sampleof a pure liquid in an open container? I. Placing it in a smallercontainer II. Increasingthe numberof molesof the liquid in the container III. Moving the container and liquid to a higher altitude (A) (B) (C) (D) (E) I only II only III only II and III only I, II, and III 27. Which of the following setsof quantumnumbers (n, I, mp, ms) bestdescribesthe valenceelectron of highestenergy in a ground-stategallium atom (atomic number3 1) ? (A) 4, 0, 0, ; (B) 4, 0, 1, ; (C) 4, 1, 1, ; (D) 4, 1, 2,; (E) 4, 2, 0, ; 28. Given that a solutionis 5 percentsucroseby mass,what additionalinformation is necessaryto calculatethe molarity of the solution? I. The density of water II. The density of the solution III. The molar massof sucrose (A) (B) (C) (D) (E) I only II only III only I andII1 II andIII 29. When an aqueoussolutionof NaOH is addedto an aqueoussolutionof potassiumdichromate, K&O,, the dichromateion is convertedto (A) CrO:(B) Cfl2- (C) Cr3+ (D) CrzO&) (E) Cr(OH)&) ReactionCoordinate 30. The energy diagram for the reactionX + Y + Z is shownabove.The additionof a catalystto this reaction would causea changein which of the indicated energy differences? (A) (B) (C) (D) (E) 1 only II only III only I and II only I, II, and III q 17B 31. H2C204+ 2 Hz0 ti 2 H30+ + C20$Oxalic acid, H2C204, is a diprotic acid with K1 = 5.36 x lo-* and K2 = 5.3 x 10m5.For the reactionabove,what is the equilibrium constant? (A) (B) (C) (D) (E) 5.36 x lo-* 5.3 x 1O-5 2.8 x lOA 1.9 x 10-l’ 1.9 x lo-l3 32. CH3CH20H boils at 78” C and CH30CH3 boils at -24” C, althoughboth compoundshavethe same composition.This difference in boiling pointsmay be attributedto a difference in (A) (B) (C) (D) (E) molecularmass density specific heat hydrogenbonding heat of combustion 33. A hydrocarbongaswith an empirical formula CH2 has a density of 1.88 gramsper liter at 0” C and 1.00 atmosphere.A possibleformula for the hydrocarbonis (B) C2H4 CC> C3He CD) Cd-b (E) Cd-&o 34. CH3-CH2-CH2-CH2-CH3 X CH3-CH2-CH2-CH2-OH HO-CH2-CH2-CH2-OH Y z Basedon conceptsof polarity and hydrogenbonding,which of the following sequences correctly liststhe compoundsabovein the order of their increasingsolubility in water? (A) (B) (C) (D) (E) 2 Y Y X X < < < < < Y< X 2 H2co3 0% H3BO3 09 H2so3 4 HCl(g) + 02(g) * 2 Cl,(g) + 2H&?) Equal numbersof molesof HCl and O2 in a closed systemare allowedto reach equilibrium as representedby the equationabove.Which of the following mustbe true at equilibrium? I. [HCI] mustbe lessthan [Cl,]. II. PCls(g) + energy III. Some PC13and Cl2 are mixed in a containerat 200” C and the systemreachesequilibrium accordingto the equationabove.Which of the following causesan increasein the number of molesof PCls presentat equilibrium? (A) (B) (C) (D) (E) I. Decreasingthe volume of the container II. Raisingthe temperature III. Adding a mole of He gas at constantvolume (A) (B) (C) (D) (E) H3PQ 51. 0.1 A4CuSO4 0.1 it4 KOH 0.1 M BaC& 0.1 MI-IF 0.1 M HNO3 PC&(g > + C12(g) @ 48. (A) I only II only I and III only II and III only I, II, and III 121 II [02] mustbe greater than [HCl]. [Cl,] must equal [H,O]. I only II only I and III only II and III only I, II, and III 59. When a 1.00~gramsampleof limestonewas dissolvedin acid, 0.38 gram of CO* was generated. If the rock containedno carbonateother than CaC03, what was the percentof CaC03 by massin the limestone? 63. What is the maximum massof copper that could be plated out by electrolyzingaqueousCuC12for 16.0 hoursat a constantcurrentof 3.00 amperes? (1 faraday = 96,500 coulombs) (A) 28 grams (B) 57 grams (C) 64 grams (D) 114 grams (E) 128 grams (A) 17% (B) 51% (C) 64% (D) 86% (E) 100% 60. 12(g) + 3 Cl2(g) + 2 ICl,(g) According to the data in the table below, what is the value of AH0 for the reactionrepresented above? Bond AverageBond Energy (kilojoules/mole) I-I Cl-Cl I-Cl 149 239 208 64. At 25” C, a sampleof NH3 (molar mass 17 grams) effusesat the rate of 0.050 mole per minute. Under the sameconditions,which of the following gases effusesat approximatelyone-half that rate? (A) (B) (C) (D) (E) O2 (molar mass32 grams) He (molar mass4.0 grams) CO2 (molar mass44 grams) Cl, (molar mass71 grams) C& (molar mass 16 grams) 65. Barium sulfate is LEAST solublein a O.Ol-molar solutionof which of the following? (A) -860 kJ (B) -382 kJ (C) +180 kJ (D) +450 kJ (E) +1,248 kJ (A) A12(S04)3 (W (Nb)2S04 (C> Na2S04 0) NH3 (E) BaC12 61. A l-molar solutionof which of the following salts has the highestpH ? (A) NflO3 @I Na2C03 (C> 66. What is the pH of a 1.0 x 10-2-molarsolutionof HCN ? (For HCN, Ka = 4.0 x lo-“.) (A) 10 (B) Between 7 and 10 WC1 (C) 7 (D) Between 4 and 7 (E) 4 (D) NaHSO‘, (E) Na2SQ 62. The electron-dotstructure(Lewis structure)for which of the following moleculeswould havetwo unsharedpairs of electronson the central atom? (A) H2S (B) NH3 Cl cH4 (D) HCN (E) COz n 23 n 67. SubstancesX and Y that were in a solutionwere separatedin the laboratory using the techniqueof fractionalcrystallization.This fractionalcrystallization is possiblebecausesubstances X and Y have different (A) (B) (C) (D) (E) 70. To determinethe molar massof a solid monoprotic acid, a studenttitrated a weighedsampleof the acid with standardizedaqueousNaOH. Which of the following could explain why the student obtaineda molar massthat was too large? boiling points melting points densities crystalcolors solubilities I. Failure to rinse all acid from the weighingpaper into the titration vessel II. Addition of more water than was neededto dissolvethe acid III. Addition of somebasebeyondthe equivalence point 68. Which of the following moleculeshas a dipole momentof zero? (A) (B) (C) (D) (E) C6H6(benzene) NO SO1 NH3 HS (A) (B) (C) (D) (E) 71. . . . Fe(OH)z + . . . O2 + . . . Hz0 + . . . Fe(OH)3 If 1 mole of O2 oxidizesFe(OH)2 accordingto the reactionrepresentedabove,how many molesof Fe(OH)j can be formed? 69. Correct proceduresfor a titration include which of the following? I. Draining a pipet by touchingthe tip to the side of the containerusedfor the titration II. Rinsingthe buret with distilledwaterjustbefore filling it with the liquid to be titrated III. Swirling the solutionfrequentlyduringthe titration (A) (B) (C) (D) (E) I only III only I and II only II and III only I, II, and III (A) (B) (C) (D) (E) I only II only I and III only II and III only I, II, and III n 24 n 2 3 4 5 6 72. The nuclide 249 ,,Cm is radioactiveand decaysby the loss of one beta (p-) particle. The productnuclide is 74. A solutionof calcium hypochlorite,a common additiveto swimming-poolwater, is (A) basicbecauseof the hydrolysisof the OCl- ion (B) basic becauseCa(OH)2 is a weak and insoluble base (C) neutral if the concentrationis kept below 0.1 molar (D) acidic becauseof the hydrolysisof the Ca” ions (E) acidic becausethe acid HOC1 is formed (A) ‘;;Pu (B) “z:Arn (C) ‘ZiCrn (D) ‘;;&-I 73. 2 sol(g) + 02(g) + 2 SO3(g) When 0.40 mole of SO?and 0.60 mole of 02 are placed in an evacuatedl.OO-liter flask, the reaction representedaboveoccurs.After the reactants and the productreach equilibrium and the initial temperatureis restored,the flask is found to contain 0.30 mole of S03. Basedon theseresults,the equilibrium constant,K,, for the reactionis 75. A direct-currentpower supplyof low voltage(less than 10 volts) has lost the markingsthat indicate which outputterminal is positiveand which is negative.A chemistsuggeststhat the power supply terminalsbe connectedto a pair of platinumelectrodes that dip into O.l-molar KI solution.Which of the following correctly identifies the polaritiesof the power supplyterminals? (A) 20. (B) 10. (C) 6.7 (D) 2.0 (E) 1.2 (A) A gas will be evolvedonly at the positiveelectrode. (B) A gas will be evolvedonly at the negativeelectrode. (C) A brown color will appearin the solutionnear the negativeelectrode. (D) A metal will be depositedon the positiveelectrode. (E) None of the methodsabovewill identify the polaritiesof the power supplyterminals. c STOP END OF SECTION I IF YOU FINISH BEFORE TIME IS CALLED, YOU MAY CHECK YOUR WORK ON THIS SECTION. DO NOT GO ON TO SECTION II UNTIL YOU ARE TOLD TO DO SO. n 25 n