Initials:_______ 1 Chemistry 115a PLEASE PRINT YOUR NAME IN BLOCK LETTERS Practice Exam 2 Name: ______________________________ Dr. Jessica Parr Instructions: 1. You must show work to receive credit. 2. There are 10 problems on 8 pages. Please count them before you begin. A periodic table and some useful equations can be found on the last page. 3. You MUST use black or blue ink. (No whiteout, no erasable ink, no pencil.) 4. Your exam will be scanned. Write your initials in the top right hand corner of each page. Points deducted if not done. 5. You must submit all pages to the proctors, including the periodic table page. 6. Only a non-progammable calculator may be used on Chem 115a/b exams. 7. Turn off cell phones and other electronic communication devices and put them away, out of sight. They may not be taken out of your bag during the exam. 8. When time is called, stop working on your exam immediately, turn the exam over and pass it to the aisle. 9. Good luck!! =) Please Sign Below: I certify that I have observed all the rules of Academic Integrity while taking this examination. Signature: _______________________________________________________________ Last 4 Digits of USC ID:____ ____ ____ ____ Question Points Score Grader 1 8 2 12 3 12 4 10 5 8 6 10 7 8 8 12 9 12 10 8 Total 100 First Letter of Last NameInitials:_______ 2 1. (8 pt) What precipitate, if any, will result from the mixing of the following aqueous solutions? If no precipitate forms write NONE. a. BaCl2 (aq) + K2SO4 (aq) __________________ b. Cr(NO3)3 (aq) + (NH4)2CO3 (aq) __________________ c. LiCl (aq) + Pb(NO3)2 (aq) __________________ d. KNO3 (aq) + NH4OH (aq) __________________ 2. (12 pt) Identify the oxidation states on all of the atoms in the reactants and products of the following oxidation-reduction reaction. Identify what is being oxidized, what is being reduced, as well as the oxidizing and reducing agents. 2 PF2I (l) + 2 Hg (l)  P2F4 (g) + Hg2I2 (s) Reactants: P: ______ F: ______ I: ______ Hg: ______ Products: P: ______ F: ______ I: ______ Hg: ______ Oxidized: __________________ Reduced: __________________ Oxidizing Agent: __________________ Reducing Agent: __________________Initials:_______ 3 3. (12 pt) A 10.96 g solid sample of tin(II) combined with an unknown halide is dissolved in 235 mL of a 0.112 M Na3PO4 solution and reacts completely to form solid tin(II) phosphate. a. What mass of tin was in the solid sample? b. What is the molar mass of the tin(II) halide compound? c. Identify the halide.Initials:_______ 4 4. (10 pt) An acid solution is 0.100 M in HBr and 0.150 M in H3PO4. What volume of a 0.075 M NaOH solution would completely neutralize all the acid in 250.0 mL of this solution? What is the concentration of bromide ion in the final solution? 5. (8 pt) A 118 mL flask is evacuated and found to have a mass of 97.129 g. When the flask is filled with 768 torr of helium gas at 35oC, it has a mass of 97.171 g. Was the helium gas pure? Show work to support your answer.Initials:_______ 5 6. (10 pt) When hydrochloric acid is poured over potassium sulfide, 42.9 mL of hydrogen sulfide gas is produced at a pressure of 752 torr at a temperature of 25.8oC. a. Write the balanced equation for this reaction. b. How many grams of potassium sulfide reacted? 7. (8 pt) It took 12.6 minutes for 475 mL of Xe gas to effuse through a porous barrier. How long will it take for 525 mL of SO3 gas to effuse under the same conditions?Initials:_______ 6 8. (12 pt) A 275 mL flask contains pure helium at a pressure of 752 torr. A second flask with a volume of 475 mL contains pure argon at a pressure of 722 torr. If the two flasks are connected through a stopcock and the stopcock is opened, what are the partial pressures and mole fractions of each gas when the stopcock is open? What is the total pressure in the container when the stopcock is open? 9. (12 pt) A flask at room temperature contains exactly equal amounts (in moles) of nitrogen and xenon. Assuming ideal behavior, answer the following questions. Circle the correct answer. a. Which of the two gases exerts the greater partial pressure? N2 Ar both are the same b. The atoms or molecules of which gas have the greatest average velocity? N2 Ar both are the same c. The molecules or atoms of which gas have the greatest average kinetic energy? N2 Ar both are the same d. If a small hole were opened in the flask, which gas would effuse more quickly? N2 Ar both are the sameInitials:_______ 7 10. (8 pt) Find the numerical difference between the ideal and van der Waals pressures of 0.356 mol of water vapor at a temperature of 105oC in a 250. mL container. a = 5.46 L2*atm/mol2 and b = 0.0305 L/molInitials:_______ 8 I VIII 1 H 1.008 II III IV V VI VII 2 He 4.003 3 Li 6.941 4 Be 9.012 5 B 10.81 6 C 12.01 7 N 14.01 8 O 16.0 9 F 19.00 10 Ne 20.18 11 Na 22.99 12 Mg 24.31 13 Al 26.98 14 Si 28.09 15 P 30.97 16 S 32.07 17 Cl 35.45 18 Ar 39.95 19 K 39.10 20 Ca 40.08 21 Sc 44.969 22 Ti 47.88 23 V 50.94 24 Cr 51.996 25 Mn 54.9380 26 Fe 55.847 27 Co 58.9332 28 Ni 58.69 29 Cu 63.546 30 Zn 65.377 31 Ga 69.72 32 Ge 72.59 33 As 74.9216 34 Se 78.96 35 Br 79.90 36 Kr 83.80 37 Rb 85.47 38 Sr 87.62 39 Y 88.91 40 Zr 91.22 41 Nb 92.91 42 Mo 95.94 43 Tc (99) 44 Ru 101.1 45 Rh 102.9 46 Pd 106.4 47 Ag 107.9 48 Cd 112.4 49 In 114.8 50 Sn 118.7 51 Sb 121.8 52 Te 127.6 53 I 126.9 54 Xe 131.3 55 Cs 132.9 56 Ba 137.3 57 La 138.9 72 Hf 178.5 73 Ta 180.9 74 W 183.85 75 Re 186.2 76 Os 190.2 77 Ir 192.2 78 Pt 195.09 79 Au 197.0 80 Hg 200.6 81 Tl 204.4 82 Pb 207.2 83 Bi 209.0 84 Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra 226.0 89 Ac 227.0 104 Rf (261) 105 Db (262) 106 Sg (263) 107 Bh (262) 108 Hs (265) 109 Mt (268) Lanthanides 58 Ce 140.1 59 Pr 140.9 60 Nd 144.2 61 Pm (145) 62 Sm 150.4 63 Eu 151.96 64 Gd 157.3 65 Tb 158.9 66 Dy 162 67 Ho 164.9 68 Er 167.3 69 Tm 168.9 70 Yb 173.0 71 Lu 175 Actinides 90 Th 232.0 91 Pa 231.0 92 U 238.0 93 Np 237.0 94 Pu (244) 95 Am (243) 96 Cm (247) 97 Bk (247) 98 Cf (251) 99 Es (252) 100 Fm (257) 101 Md (258) 102 No (259) 103 Lr (26) Useful Equations and Constants: PV = nRT R = 0.08206