2045 CHM Exam 1
(Form Code A)
January 29, 2008
READ THESE INSTRUCTIONS COMPLETELY: Please bubble in (with a #2 pencil) your Last Name (left justified, spaces at the end) and your First and Middle initials (in FI and MI, respectively), on the answer sheet provided. Also bubble in your CHM2045 section number (in Section), and UF ID (in ID Number, leave one space at the end, no hyphen). Leave special codes blank and enter the test form code above. Incomplete or incorrect information will result in an unrecoverable loss of score. Read the entire exam and answer the following 25 questions for a total of 250 points in the context and conventions of our lectures. Work alone, do not talk, and do not share anything with anyone around you. Bubble all answers carefully on the answer sheet. Coding accuracy on the answer sheet is entirely the responsibility of the student; Illegible or incorrect marks will not be credited. Please sign the back of the answer sheet and turn it in before the end of the exam period. Late papers will not be collected. Good Luck! 1. How many atoms of oxygen are in 35.7 g of anhydrous copper(II) sulfate? 1) 1.35 x 1023 atoms 2) 5.39 x 1023 atoms 3) 4.57 x 1023 atoms 4) 2.15 x 1025 atoms 5) 2.15 x 1023 atoms 2. Which of the following represents the largest volume? 1) 10,000 L 2) 1000 pL 3) 100 mL 4) 10 nL 5) 10 cm3
3. Manganese makes up 1.3 x 104 percent by mass of the elements found in the healthy male body of a certain mammal. If 0.11 g of manganese is found, how much does the average male body weight? (1 kg = 2.2 lb) 1) 186 lb 2) 1.86 lb 3) 84.6 lb 4) 195 lb 5) 116 lb 4. How many electrons are in a single 56Fe3+ ion? 1) 53 2) 23 3) 26 4) 30 5) none of these
5. Copper has two naturally occurring isotopes, 63Cu (isotopic mass 62.9396 u) and 65Cu (isotopic mass 64.9278 u). If copper has an atomic mass of 63.546 u, what is the percent abundance of 65Cu in a naturally occurring sample of copper? 1) 15.3% 2) 30.5% 3) 61.0% 4) 69.5% 5) 91.5% 6. Phosphorus has the molecular formula P4 and sulfur has the molecular formula S8. How many grams of phosphorus contain the same number of molecules as 6.41 g of sulfur? 1) 3.09 g 2) 3.21 g 3) 6.19 g 4) 6.41 g 5) none of these 7. A compound contains 49.48% carbon, 5.191% hydrogen, 28.87% nitrogen, and 16.48% oxygen by mass and has a molar mass of 194.2 g/mol. Determine the molecular formula of the compound. 1) C4H5N2O 2) C10H12N4O2 3) C8H8N3O3 4) C8H9N5O 5) C8H10N4O2 8. A 1.013-g sample of ZnSO4xH2O is dissolved in an aqueous solution of BaCl2. The pure BaSO4 precipitate is filtered out of solution, dried, and its mass is determined to be 0.8223 g. What is the value of x in ZnSO4xH2O? 1) 1 2) 3 3) 5 4) 7 5) 9 9. What is the correct value of X in the balanced chemical equation below? Fe2O3(s) + X HNO3(aq) 2 Fe(NO3)3(aq) + Y H2O(l) 1) 1 2) 2 3) 4 4) 6 5) 8 10. From the Thermochemical data on the data sheet, calculate the change in enthalpy for the following process: P4O10 (s) + 6 H2O(l) 4 H3PO4(s) 1) 313 kJ 2) 487 kJ 3) 313 kJ 4) 487 kJ 5) 291 kJ 11. A 1.562-g sample of the hydrocarbon C7H16 is completely combusted in an excess of O2. What mass of CO2 is produced? 1) 0.686 g 2) 1.31 g 3) 3.49 g 4) 3.56 g 5) 4.80 g 12. A hot 625 g chunk of iron is plunged into 500. g of water in an insulated container. The temperature of the water increases from 24 to 75 C. Using the Thermodynamic data from the data sheet, what must have been the initial temperature of the iron? 1) 403 C 2) 454 C 3) 116 C 4) 760 C 5) 379 C
13. What volume (mL) of aqueous 0.75 M Ca(NO3)2 solution must be diluted with pure water to produce 1.00 L of a solution with 0.45 M NO3 ? 1) 100 mL 2) 167 mL 3) 300 mL 500 4) mL 5) 600 mL 14. How many mL of 1.0 M MgCl2 solution would need to be added to an excess volume of aqueous AgNO3 solution to precipitate 20. g of AgCl(s)? 1) 20 mL 2) 70 mL 3) 140 mL 4) 210 mL 5) 280 mL 15. A 5.000 g sample of an unknown soluble metal chloride is dissolved in water. If all of the chloride in the sample is precipitated as AgCl(s) when 70.90 mL of 0.2010 M AgNO3 is added to the solution, what is the mass percentage of chloride in the unknown metal chloride? 1) 50.55% 2) 10.10% 3) 1.425% 4) 20.33% 5) 45.55% 16. Express the unit of heat in SI base units. 1) J K-1 g-1 2) m2 s-2 K-1 3) J K-1 mol-1 4) kg m2 s-2 5) none of these
17. In the electrolysis of liquid water, what gas is formed at the negative electrode by the passage of electric current? 1) H2 2) O2 3) H2O 4) H2O2 5) O3 18. Consider the complete combustion of 1.2345 g of C6H12 in excess oxygen gas. What is the closest value of the mass of oxygen gas consumed in this reaction? 1) 1.4668 g 2) 0.4694 g 3) 4.2244 g 4) 3.0510 g 5) 2.1200 g 19. What is the net ionic equation for the precipitation of solid lead(II) chloride resulting from mixing aqueous solutions of lead(II) nitrate and magnesium chloride? 2) Pb+(aq) + Cl(aq) PbCl(s) 1) Pb2+(aq) + 2Cl(aq) PbCl2(s) 3) PbNO3(aq) + MgCl2(aq) PbCl2(s) 4) Pb(NO3)2(aq) + MgCl2(aq) PbCl2(s) 5) none of these 20. What is closest value to the mass percent of oxygen in potassium perchlorate? 1) 0.00% 2) 66.7% 3) 46.2% 4) 63.2 % 5) 60.0% 21. A 123.34 g block of Niobium (Nb) at temperature of 372.15 K is dropped into an insulated cup containing 153.30 g of water. If the initial temperature of the water is 2.000 oC, what is the closest value to the final temperature of the water after thermal equilibrium is attained? (see data sheet for useful Thermodynamic information) 1) 6.77 oC 2) 35.92 oC 3) 94.23 oC 4) 1.892 oC 5) 20.21 oC 22. From the data on the data sheet only, what is the closest value to the Heat of Formation of CS2 (liq) ? 1) 90.1 kJ/mol 2) 90.1 kJ/mol 3) 386.9 kJ/mol 4) 45.1 kJ/mol 5) 1032. kJ/mol 23. From the data on the data sheet only, what is the closest value to the molar Enthalpy change for the reaction: CS2 (liq) + 3 Cl2 (g) CCl4 (liq) + S2Cl 2 (liq) 1) 148.5 kJ/mol 2) 283.7 kJ/mol 3) 5.2 kJ/mol 4) 400.1 kJ/mol 5) 413.3 kJ/mol 24. The complete combustion of 3.1371 g of an unknown compound with the formula C5H13O liberates 967.2 J of heat. What is the closest value to the standard molar Heat of Combustion of the unknown compound? 1) 27.5 kJ/mol 2) 27488 kJ/mol 3) 967.2 kJ/mol 4) 27.5 kJ/mol 5) 32.7 kJ/mol 25. How many grams of phosphorus trichloride can be produced if 24.0 grams of phosphorus (P4) is allowed to react with 91.5 grams of chlorine gas? 1) 106 g 2) 26.6 g 3) 118 g 4) 177 g 5) 206 g
(The following data will be provided on the back of the Periodic Tables given to students) Thermochemical Data: CO2 (g) = C(s, graphite) + O2 (g) Hrxno = +393.5 kJ/mol CS2 (liq) + 3 O2 (g) = CO2 (g) + 2 SO2 (g) Hrxno = 1077.2 kJ/mol S8 (s) + 4 Cl2 (g) = 4 S2Cl2 (liq) Hrxno = 232.8 kJ/mol C (s, graphite) + 2 Cl2 (g) = CCl4 (liq) Hrxno = 135.4 kJ/mol 1/8 S8 (s) + O2 (g) = SO2 (g) Hrxno = 296.8 kJ/mol SO2 (g) + Cl2 (g) = SO2Cl2 (liq) Hrxno = +97.3 kJ/mol CCl4 (liq) + O2 (g) = COCl2 (g) + Cl2O (g) Hrxno = 5.2 kJ/mol 2 H2 (g) + O2 (g) = 2 H2O(liquid) Hrxno = 571.6 kJ/mol P4 (solid, white) + 5 O2 (gas) = P4O10 (s) Hrxno = 3110 kJ/mol P4 (solid, white) + 3/2 H2 (gas) + 2 O2 (gas) = H3PO4 (s) Hrxno = 1279 kJ/mol Specific Heat Capacity (H2O(liquid) ) = 4.184 J K-1g-1 Specific Heat Capacity (Nb(s) ) = 0.2691 J K-1g-1 Specific Heat Capacity (Fe(s) ) = 0.450 J K-1g-1 Avogadro's Number: NA = 6.02214 x 1023 mol-1