Lab Day and Time: Instructions. 1. Do not open the exam until you are told to start.

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1 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 In-Class EC 2.5 Attendance 3 Total 100 1

2 Multiple Choice Unless otherwise directed, choose the single best answer for each question. Some of the chemical equations will be balanced and some will not. Each question is worth three points. 1. Using the chemical equation below, calculate the number of moles of CuO that will be produced if 3.25 moles of O 2 react with excess Cu. Cu(s) + O 2 (g) CuO(s) a.) 3.25 mol CuO b.) 1.63 mol CuO c.) 9.75 mol CuO d.) 6.50 mol CuO When methane gas is combusted, it reacts with O 2 (g) and produces CO 2 (g) and H 2 O(g). The balanced chemical equation for this reaction is shown below. Use this equation and the diagrams below to answer the following three questions. CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g) hydrogen oxygen carbon Before Reaction 2. Which compound is the excess reactant? After Reaction a.) CH 4 b.) O 2 c.) CO 2 d.) H 2 O 3. How many molecules were in the container before the reaction started? a.) 3 d). 7 b.) 5 c.) 6 4. If the size of the container remained the same and the pressure increased over the course of the reaction, which of the statements below could explain why the pressure increased. a.) The pressure increased because the number of gas particles decreased. b.) The pressure increased because the number of gas particles increased. c.) The pressure increased because the temperature decreased. d.) The pressure increased because the temperature increased. 2

3 5. A solution is made by dissolving 14.7 g of H 2 SO 4 in enough water to make ml of solution. What is the molarity of this H 2 SO 4 solution? a.) 1.33 M b.) M c.) M d.) M 6. A small beaker containing deionized water and an unknown mass of Al(OH) 3 (s) is found in the laboratory. Realizing that Al(OH) 3 is a base you decide to titrate the solid with M HCl(aq). If the titration requires ml of the HCl to reach the end point, what mass of Al(OH) 3 was in the beaker? M.M. of Al(OH) 3 = g / mole Al(OH) 3 a.) g b.) g c.) g d.) g 7. According to the balanced chemical equation shown below, if 13 g of C 2 H 2 are produced during a reaction, how many grams of H 2 O must have reacted? CaC 2 (s) + 2H 2 O(g) Ca(OH) 2 (s) + C 2 H 2 (g) Molar Mass (g/mole) a.) 4.5 g H 2 O b.) 9.0 g H 2 O c.) 4.8x10 2 g H 2 O d.) 18 g H 2 O 3

4 8. You have ml of a 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 M NaCl. How much water must have evaporated? a.) ml b.) ml c.) ml d.) ml 9. When NH 3 is prepared from the reaction of g of H 2 with excess N 2, the actual yield of NH 3 is g. Calculate the percent yield. N 2 (g) + 3H 2 (g) 2NH 3 (g) Molar Mass (g/mole) a.) 6.667% b.) 88.10% c.) 20.15% d.) 82.00% 10. A g sample of helium is held in a container. The pressure of helium inside the container is 635 mmhg and the temperature is 19.5 C. What is the volume of the container? a.) 668 L b.) 167 L c.) 11.1 L d.) L 4

5 11. You need moles of HCl for an experiment. What volume of M HCl do you need to provide you with the proper amount of HCl? a.) L b.) 2.47 L c.) L d.) L 12. 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 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) kj Molar Mass (g/mole) How much energy will be released when 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 End of Multiple Choice 5

6 13. 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.) What have you done when you reach the end point? (2 points) c.) When you do your calculations what do you assume? (3 points) 14. A sample of Co reacts with ml of M HI to produce H 2 (g) as described in the balanced chemical equation below. The H 2 (g) is collected in a container over water at C. The volume of the collected gas is ml. Co(s) + 2HI(aq) CoI 2 (aq) + H 2 (g) a.) How many moles of H 2 gas are collected? (4 points) b.) What is the total pressure (in mmhg) inside the container holding the H 2 gas? (9 points) 6

7 15. A sample of M KOH is titrated with M H 2 SO 4. The balanced equation for the titration reaction is shown below. 2KOH(aq) + H 2 SO 4 (aq) 2H 2 O(l) + K 2 SO 4 (aq) a.) If the titration requires ml of the H 2 SO 4 solution to reach the end point, what was the volume (in ml) of the sample of KOH? (8 points) b.) If 20.0 ml of M HCl was added to the sample of KOH before you started your titration, would the volume of H 2 SO 4 needed to reach the end point be larger, smaller, or no different than the value given above? (2 points) 16. 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. (6 points) NAME FORMULA HBr lead(ii) oxalate Ba(NO 2 ) Which of the two colors of light listed below is the least energetic? Circle your answer. (3 points) yellow light or blue light 7

8 18. 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) a.) If you start with 24.8 g of P 4 and 25.7 g of S 8, what mass of P 4 S 3 will you produce? You must use dimensional analysis and show all your work to receive full credit. (15 points) b.) What mass of each reactant will be left after the reaction is complete? (6 points) 8

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11 Conversion Factors, Constants, and Periodic Table Avogadro s Number: x particles/mole Pressure Conversion: 760 mmhg (torr) = 1 atm Ideal Gas Constant: L atm mol K Temperature conversion: T [K] = T [ C] Percent Yield: actual yield % yield 100% theoretical yield Vapor Pressure of Water at Various Temperatures Temperature ( C) Vapor Pressure (mmhg) Dilution: M 1 V 1 =M 2 V 2 Gas Equations: P A P tot χ A PV nrt 1 H Li Na K Rb Cs Fr (223) 4 Be Mg Ca Sr Ba Ra Sc Y La Ac Ti Zr Hf Rf (261) 23 V Nb Ta Db (262) 24 Cr Mo W Sg (263) 25 Mn Tc (98) 75 Re Bh (262) 26 Fe Ru Os Hs (265) 27 Co Rh Ir Mt (266) 28 Ni Pd Pt Uun (269) 29 Cu Ag Au Uuu (272) 30 Zn Cd Hg Uub (277) 5 B Al Ga In Tl C Si Ge Sn N P As Sb O S Se Te F Cl Br I He Ne Ar Kr Xe Pb Bi Po At Rn (209) (210) (222) Ce Th Pr Pa Nd U Pm (145) 93 Np (237) 62 Sm Pu (244) 63 Eu Am (243) 64 Gd Cm (247) 65 Tb Bk (247) 66 Dy Cf (251) 67 Ho Es (252) 68 Er Fm (257) 69 Tm Md (258) 70 Yb No (259) 71 Lu Lr (260) 11