Name: Lab Day and Time: Instructions 1. Do not open the exam until you are told to start. 2. This exam is closed note and closed book. You are not allowed to use any outside material while taking this exam. 3. Use the spaces provided to write down your answers. To receive full credit, you must show all work. Do not write answers on any other pieces of paper. If you need more room, write on the back of the exam and be sure to include a note describing where the work is located. 4. When solving numerical problems, make sure you include the proper units in your final answer. 5. If a question asks for a response in sentence or paragraph form, make sure you respond in that format. 6. Useful data for the exam and a periodic table are provided on the last page of the exam. Carefully tear out these sheets if you wish. Page # Points possible Points awarded 2-6 (M.C.) 48 6 10 7 18 8 21 Attendance 3 Extra Credit 2 Total 100 1
Multiple Choice Unless otherwise directed, choose the single best answer for each question. 1. In a laboratory at UCI, a sample of gas is collected in the manometer shown on the right at a temperature of -76.0ºC. If the whole apparatus (i.e. the manometer and gas) is then transported to the top of Mount Everest (the highest elevation on Earth), what will happen to the height of the mercury column that is in contact with the collected gas (i.e. the left hand side of the U- tube)? The temperature at the top of Mount Everest is also -76.0ºC. a.) the height will increase b.) the height will decrease c.) the height will stay the same d.) None of the above. P Gas P atm 2. A 2.36 mole sample of K 3 PO 4 is dissolved in enough water to make 325 ml of solution. What is the concentration of potassium ions in this solution? a.) 7.26x10-3 M b.) 7.26 M c.) 21.8 M d.) 2.36 M 3. Given the balanced reaction below, how many moles of H 2 SO 4 are required to produce 2.0 moles of I 2? Assume all of the other reactants are in excess. 2 KMnO 4 (aq) + 10 KI(aq) + 8 H 2 SO 4 (aq) 6 K 2 SO 4 (aq) + 2 MnSO 4 (aq) + 5 I 2 (aq) + 8 H 2 O(l) a.) 0.80 mol b.) 1.3 mol c.) 3.2 mol d.) 4.0 mol e.) 1.6 mole 4. A sample of nitrogen gas (N 2 ) is contained in a balloon at STP. If the balloon contains 2.00 mole of N 2 (g), what is the volume of the balloon? a.) 44.8 L b.) 1.64 L c.) 2.05 L d.) 22.4 L 2
The diagram below depicts the collection of N 2 (g),o 2 (g), and Ar(g) over water. Use the diagram to answer the following two questions. N 2 (g) O 2 (g) Ar(g) Temperature of gases and water = 50.00 C H 2 O(l) 5. If the partial pressure of N 2 is 0.24 atm., the partial pressure of O 2 is 0.50 atm., and the partial pressure of Ar is 0.49 atm., what is the mole fraction of O 2 (g) in the mixture of gases? a.) 1.23 b.) 0.50 c.) 0.41 d.) 0.37 6. If some O 2 (g) is added to the container, what will happen to the frequency of collisions between the gas particles? a.) The frequency of collisions will decrease. b.) The frequency of collisions will increase. c.) The frequency of collisions will not change. d.) It is impossible to tell what will happen to the frequency of collisions. 7. A 20.00 ml solution of 0.3000 M H 2 SO 4 is titrated with a 0.2500 M solution of KOH. What volume of KOH must be added to react with all of the H 2 SO 4? a.) 24.00 ml b.) 12.00 ml c.) 48.00 ml d.) 90.00 ml e.) None of the above 3
8. A 5.95-g sample of AgNO 3 is reacted with excess BaCl 2 according to the equation below. 2AgNO 3(aq) + BaCl 2(aq) 2AgCl(s) + Ba(NO 3) 2 (aq) Molar Mass (g/mol) 169.8731 208.232 143.3209 261.337 If 3.49 g of AgCl is obtained from the reaction, what is the percent yield of AgCl? a.) 34.8% b.) 58.7% c.) 46.3% d.) 69.5% 9. Use the unbalanced chemical equation below to answer the following question. How many molecules of Cl 2 are required to react with a 4 atoms of iron? Fe(s) + Cl 2 (g) FeCl 3 (s) a.) 6 molecules Cl 2 b.) 4 molecules Cl 2 c.) 3 molecules Cl 2 d.) 2 molecules Cl 2 10. What is the volume of a 2.00 M NaOH solution needed to make 150.0 ml of a 0.800 M NaOH solution? a.) 375 ml b.) 150. ml c.) 120. ml d.) 90.0 ml e.) 60.0 ml 4
11. When a sample of iron is added to a sample of oxygen, 12.5 g of Fe 2 O 3 is produced. Calculate the mass of oxygen that reacted. 4 Fe(s) + 3 O 2 (g) 2 Fe 2 O 3 (s) Molar Mass (g/mol) 55.847 31.9988 159.692 a.) 3.76 g b.) 12.5 g c.) 4.11 g d.) 7.86 g e.) 9.56 g 12. A 6.35 L sample of carbon monoxide gas is collected at 328.15 K and 0.892 atm. What volume will the same sample of gas occupy at 1.05 atm and 293.15 K? a.) 4.82 L b.) 1.96 L c.) 5.46 L d.) 6.10 L e.) 22.4 L 13. You have 100.0 ml of a 0.2500 M solution of NaCl sitting in a beaker. After several days you test the solution and find that it is 0.3125 M NaCl. How much water must have evaporated? a.) 10.00 ml b.) 20.00 ml c.) 80.00 ml d.) 90.00 ml 14. How many liters of gas is 0.3855 moles of nitrogen (N 2 ) at 1.026 atm. and 38.0 C? a.) 10.1 L b.) 1.17 L c.) 9.60 L d.) 269 L 5
15. A particular balloon is designed to be inflated to a volume of no more than 2.40 L. If the balloon is filled with 1.96 L of H 2 (g) at sea-level and then rises to an altitude at which the atmospheric pressure is 650. mmhg, will the balloon burst? You will need to determine the pressure at sea-level, what is a good assumption for the pressure at sea-level? Assume the temperature remains constant. a.) No, the balloon will not burst. b.) Yes, the balloon will burst c.) It is impossible to tell. 16. Calculate the mass of silver nitrate (in grams) in 145 ml of a 4.31 M AgNO 3 solution. The molar mass of AgNO 3 is 169.8731 g/mol. a.) 5.05 g b.) 24.6 g c.) 106 g d.) 170. g 17. In the table below, the name or formula for a chemical compound is given. Fill in the table with the corresponding name or formula of the chemical compound. (10 points) NAME FORMULA HIO 3 lead(ii) cyanide PCl 5 Sr(C 2 H 3 O 2 ) 2 sodium sulfite 6
18. The reaction of potassium superoxide, KO 2, is used in life-support systems to replace the CO 2 (g) in expired air with O 2 (g). A balanced chemical equation for this process is shown below. 4 KO 2 (s) + 2 CO 2 (g) 2 K 2 CO 3 (s) + 3 O 2 (g) Molar Mass (g/mole) 71.0971 44.010 138.206 31.9988 a.) If you start with 32.2 g of KO 2 and 14.5 g of CO 2, what mass of O 2 will you generate? (14 points) b.) How much of each reactant will be left after the reaction is complete? (4 points) 7
19. A 18.15 ml sample of H 3 AsO 4 is titrated with 0.2365 M Ca(OH) 2. The balanced chemical equation for the titration is shown below. 2H 3 AsO 4 (aq) + 3Ca(OH) 2 (aq) 6H 2 O(l) + Ca 3 (AsO 4 ) 2 (aq) a.) If the titration requires 28.32 ml of the Ca(OH) 2 solution to reach the equivalence point, how many moles of H 3 AsO 4 were in the original solution? (8 points) b.) What was the molarity of the original H 3 AsO 4 solution? (3 points) c.) If the end point of the titration was dark pink in color, would the value for the calculated molarity be too large, too small, or unaffected? (3 points) 20. A sample of H 2 gas is collected over water at 30.00ºC in a small container. If 0.0965 grams of H 2 (g) is collected and the volume of the H 2 (g) is 1.93 L, what is the total pressure inside the container holding the H 2 (g) in atmospheres? (7 points) 8
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Conversion Factors, Constants, and Periodic Table Avogadro s Number: Pressure Conversion: Ideal Gas Constant: Temperature conversion: 6.022 x 10 23 particles/mole 760 mmhg (torr) = 1 atm L atm 0.08206 mol K L mmhg 62.36 mol K J 8.314 mol K T [K] = 273.15 + T [ C] Vapor Pressure of Water at Various Temperatures Temperature ( C) Vapor Pressure (mmhg) 5.00 6.54 15.00 12.79 17.00 14.53 19.00 16.48 21.00 18.65 23.00 21.07 25.00 23.76 30.00 31.82 50.00 92.51 Percent Yield: actual yield % yield = 100% theoretical yield Gas Equations: P A = P tot χ A PV = nrt 1 H 1.0079 3 Li 6.941 11 Na 22.9898 19 K 39.0983 37 Rb 85.4678 55 Cs 132.905 87 Fr (223) 4 Be 9.0122 12 Mg 24.3050 20 Ca 40.078 38 Sr 87.62 56 Ba 137.327 88 Ra 226.025 21 Sc 44.9559 39 Y 88.9059 57 La 138.906 89 Ac 227.028 22 Ti 47.88 40 Zr 91.224 72 Hf 178.49 104 Rf (261) 23 V 50.9415 41 Nb 92.9064 73 Ta 108.948 105 Db (262) 24 Cr 51.9961 42 Mo 95.94 74 W 183.85 106 Sg (263) 25 Mn 54.9380 43 Tc (98) 75 Re 186.207 107 Bh (262) 26 Fe 55.847 44 Ru 101.07 76 Os 190.2 108 Hs (265) 27 Co 58.9332 45 Rh 102.906 77 Ir 192.22 109 Mt (266) 28 Ni 58.693 46 Pd 106.42 78 Pt 195.08 110 Uun (269) 29 Cu 63.546 47 Ag 107.868 79 Au 196.967 111 Uuu (272) 30 Zn 65.409 48 Cd 112.411 80 Hg 200.59 112 Uub (277) 5 B 10.811 13 Al 26.9815 31 Ga 69.723 49 In 114.82 81 Tl 204.383 6 C 12.011 14 Si 28.0855 32 Ge 72.61 50 Sn 118.710 7 N 14.0067 15 P 30.9738 33 As 74.9216 51 Sb 121.757 8 O 15.9994 16 S 32.066 34 Se 78.96 52 Te 127.60 9 F 2 He 4.0026 10 Ne 18.9984 20.1797 17 Cl 18 Ar 35.4527 39.948 35 Br 36 Kr 79.904 83.80 53 I 54 Xe 126.904 131.29 82 83 84 85 86 Pb Bi Po At Rn 207.2 208.980 (209) (210) (222) 114 116 118 58 Ce 140.12 90 Th 232.038 59 Pr 140.908 91 Pa 231.036 60 Nd 144.24 92 U 238.029 61 Pm (145) 93 Np (237) 62 Sm 150.36 94 Pu (244) 63 Eu 151.96 95 Am (243) 64 Gd 157.25 96 Cm (247) 65 Tb 158.925 97 Bk (247) 66 Dy 162.50 98 Cf (251) 67 Ho 164.930 99 Es (252) 68 Er 167.26 100 Fm (257) 69 Tm 168.934 101 Md (258) 70 71 Yb Lu 173.04 174.967 102 103 No Lr (259) (260) 11