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 MC 39 6 20 7 20 8 18 Attendance 3 In Class Extra Credit 3 Total 100 1
Multiple Choice Unless otherwise directed, choose the single best answer for each question. When balancing chemical equations use smallest whole number coefficients. (3 points each, 6 points for #2) 1. When atoms react, they do so by gaining electrons, losing electrons, or sharing electrons. The ease with which they can do these things affects their reactivity. Based on your knowledge of effective nuclear charge, the trends in first ionization energy, the trends in atomic size, and the ways in which metals and non-metals react, which of the metals below would you expect to be the most reactive? a.) Au b.) Ba c.) W d.) Cs e.) They would all be equally reactive. 2. A 13.25 ml sample of HCl is titrated with 0.2345 M Ca(OH) 2. If the titration requires 25.36 ml of the Ca(OH) 2 solution to reach the equivalence point, how many moles of HCl were in the original solution? (6 points) a.) 0.005947 moles HCl b.) 0.01189 moles HCl c.) 0.4488 moles HCl d.) 0.8976 moles HCl 3. If 20.0 ml of 0.00300 M NaOH was added to the sample of HCl before you started your titration, would the volume of Ca(OH) 2 needed to reach the end point be larger, smaller, or no different than the value given above? a.) Larger b.) Smaller c.) No different 2
4. Certain reactions will give off or release energy when they occur. This energy can be used in a number of ways, including powering vehicles, heating homes, and cooking. The reaction shown below releases 241.8 kj of energy. Since it releases energy, energy can be listed as a product in the balanced chemical equation and can be treated like any other product in stoichiometric calculations. 2H 2 (g) + O 2 (g) 2H 2 O(g) + 241.8 kj Molar Mass (g/mole) 2.01588 31.9988 18.0153 How much energy will be released when 0.453 g of H 2 reacts with excess O 2? (A kj is just a unit of energy) a.) 242 kj b.) 27.2 kj c.) 54.3 kj d.) 110. kj When ethyne is combusted, it reacts with O 2 and produces CO 2 and H 2 O. The balanced chemical equation for this reaction is shown below. Use this equation and the diagrams below to answer the following two questions. 2C 2 H 2 (g) + 5O 2 (g) 4CO 2 (g) + 2H 2 O(g) C 2 H 2 CO 2 H 2 O Before Reaction 5. Which compound is the limiting reagent? After Reaction O 2 a.) C 2 H 2 b.) O 2 c.) CO 2 d.) H 2 O 6. What was the total number of molecules you started with before the reaction? a.) 8 b.) 7 c.) 6 d.) 5 3
7. Which of the elements below is the smallest? Al, Ga, B, K, Ca a.) Al b.) Ga c.) B d.) K e.) Ca 8. Calcium chloride is soluble in water. A 5.55 g sample of CaCl 2 is dissolved in enough water to make 110.0 ml of solution. What is the concentration of Cl - in the solution? a.) 0.00550 M b.) 0.455 M c.) 0.668 M d.) 0.909 M e.) None of the above 9. You have 100.0 ml of a 0.2500 M solution of NaCl sitting in a beaker. After several days you notice that water has evaporated and the volume has decreased. When you test the solution, you find that it is 0.3125 M NaCl. How much water must have evaporated? a.) 90.00 ml b.) 80.00 ml c.) 20.00 ml d.) 10.00 ml 4
10. A given set of d-orbitals contains how many degenerate orbitals? a.) 1 d.) 6 b.) 3 e.) 10 c.) 5 11. How many moles of lithium are needed to produce 0.60 moles of Li 3 N? Use the equation below to help you solve the problem. Li(s) + N 2 (g) Li 3 N(s) a.) 0.30 b.) 1.8 c.) 0.20 d.) 0.40 12. How many unpaired electrons does Mo contain? Use the orbital box diagram for Mo to help you answer the question. a.) 2 d.) 5 b.) 3 c.) 4 5
13. 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. (2 points) NAME FORMULA HBrO 3 a.) 14. In the space provided below give a.) the full electron configuration of the element that is underlined, b.) draw the Bohr representation of each element and c.) calculate the effective nuclear charge (Z eff ) felt by the valence electrons in each of the atoms. (10 points) Mg Si a.) b.) b.) c.) c.) d.) Which of the two elements above has the largest ionization energy? Briefly explain why that atom has the largest ionization energy of the two. (5 points) e.) Suppose both of the elements absorbed a photon of 400 nm light and had an electron promoted to an excited state, what color of light was absorbed? (3 points) 6
15. You are going to titrate a sample of HC 2 H 3 O 2 (aq) with a solution of NaOH(aq) just as you did in the second titration experiment in lab. a.) What have you done when you reach the equivalence point? (3 points) b.) How does the volume of base required to reach the end point (V end point ) differ from the volume of base required to reach the equivalence point (V equivalence point )? Use a mathematical equation to explain your answer. (3 points) 16. a.) What is condensed electron configuration for I? (3 points) b.) What is the Lewis Symbol for I? (3 points) 17. In the space provided below, draw a picture of a p-orbital. Make sure to point out the location of the nucleus. (3 points) 18. What is the condensed electron configuration of Fe 2+? Is this ion paramagnetic or diamagnetic? (5 points) 7
19. Tetraphosphorus trisulfide, P 4 S 3, is used in the heads of wooden matches. This material can be manufactured by heating a mixture of red phosphorus and sulfur. The balanced chemical equation for this process is shown below. 8P 4 (s) + 3S 8 (s) 8P 4 S 3 (s) Molar Mass (g/mole) 123.8950 256.528 220.093 a.) If you start with 24.8 g of P 4 and 25.7 g of S 8, what mass (in grams) of P 4 S 3 will you produce? You must use dimensional analysis and show all your work to receive full credit. (13 points) b.) What mass (in grams) of each reactant will be left after the reaction is complete? You must use dimensional analysis and show all of your work to receive full credit. (5 points) 8
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Conversion Factors, Constants, and Periodic Table Avogadro s Number: Pressure Conversion: 6.022 x 10 23 particles/mole 760 mmhg (torr) = 1 atm (exact) Compound AgNO 3 CaCl 2 Molar Mass 169.8731 g/mole 110.983 g/mole Ideal Gas Constant: L atm 0.08206 mol K Temperature conversion: T [K] = 273.15 + T [ C] A.Y. PercentYield: % Yield x100% T.Y. 1 H 1.0079 2 He 4.0026 3 Li 6.941 4 Be 9.0122 5 B 10.811 6 C 12.011 7 N 14.0067 8 O 15.9994 9 F 18.9984 10 Ne 20.1797 11 Na 22.9898 12 Mg 24.3050 13 Al 26.9815 14 Si 28.0855 15 P 30.9738 16 S 32.066 17 Cl 35.4527 18 Ar 39.948 19 K 39.0983 20 Ca 40.078 21 Sc 44.9559 22 Ti 47.88 23 V 50.9415 24 Cr 51.9961 25 Mn 54.9380 26 Fe 55.847 27 Co 58.9332 28 Ni 58.693 29 Cu 63.546 30 Zn 65.409 31 Ga 69.723 32 Ge 72.61 33 As 74.9216 34 Se 78.96 35 Br 79.904 36 Kr 83.80 37 Rb 85.4678 38 Sr 87.62 39 Y 88.9059 40 Zr 91.224 41 Nb 92.9064 42 Mo 95.94 43 Tc (98) 44 Ru 101.07 45 Rh 102.906 46 Pd 106.42 47 Ag 107.868 48 Cd 112.411 49 In 114.82 50 Sn 118.710 51 Sb 121.757 52 Te 127.60 53 I 126.904 54 Xe 131.29 55 Cs 132.905 56 Ba 137.327 57 La 138.906 72 Hf 178.49 73 Ta 108.948 74 W 183.85 75 Re 186.207 76 Os 190.2 77 Ir 192.22 78 Pt 195.08 79 Au 196.967 80 Hg 200.59 81 Tl 204.383 82 Pb 207.2 83 Bi 208.980 84 Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra 226.025 89 Ac 227.028 104 Rf (263) 105 Db (268) 106 Sg (271) 107 Bh (270) 108 Hs (270) 109 Mt (278) 110 Ds (281) 111 Rg (281) 112 Cn (285) 113 Nh (286) 114 Fl (289) 115 Mc (289) 116 Lv (293) 117 Ts (294) 118 Og (294) 58 Ce 140.12 59 Pr 140.908 60 Nd 144.24 61 Pm (145) 62 Sm 150.36 63 Eu 151.96 64 Gd 157.25 65 Tb 158.925 66 Dy 162.50 67 Ho 164.930 68 Er 167.26 69 Tm 168.934 70 Yb 173.04 71 Lu 174.967 90 Th 232.038 91 Pa 231.036 92 U 238.029 93 Np (237) 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 (260) 10