Final 01 - Su, Yung Final 1 Due: Dec 17 2007, midnight...

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Unformatted text preview: Su, Yung Final 1 Due: Dec 17 2007, midnight Inst: FAKHREDDINE 1 This print-out should have 50 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. Each question is worth 10 points. 001 (part 1 of 1) 6 points 1.00 mole of Al(NO 3 ) 3 contains how many oxygen atoms? The molar mass of Al(NO 3 ) 3 is 213.0 g/mol. 1. 1 . 81 10 24 atoms 2. 3 atoms 3. 5 . 42 10 24 atoms correct 4. 4 . 88 10 25 atoms 5. 1 . 63 10 25 atoms 6. 27 atoms 7. 9 atoms 8. 6 atoms Explanation: ? atoms O = 1 . 00 mol Al(NO 3 ) 3 9 mol atoms O 1 mol Al(NO 3 ) 3 6 . 022 10 23 atoms O 1 mol atoms O = 5 . 42 10 24 atoms O 002 (part 1 of 1) 6 points Which of the following ionic compounds has the wrong chemical formula? 1. KBr 2. NaO 2 correct 3. K 2 S 4. CaO 5. MgCl 2 Explanation: The sodium ion is Na 1+ and the oxide ion is O 2- . The compound should thus be Na 2 O. 003 (part 1 of 1) 6 points What is the percent yield if 4.51 moles of CH 4 produces 16 L of CO 2 at STP? CH 4 + 2O 2 CO 2 + 2H 2 O 1. 6.31% 2. 15.8% correct 3. 36.4% 4. 1.26% 5. 78.1% Explanation: n CH 4 = 4.51 mol V CO 2 = 16 L At STP we can use the standard molar volume, 22 . 4 L mol to convert L of CO 2 to moles: ? mol = 16 L 1 mol 22 . 4 L = 0 . 714 mol 0.714 moles is the actual yield. Now calculate the theoretical yield: ? mol CO 2 = 4 . 51 mol CH 4 1 mol CO 2 1 mol CH 4 = 4 . 51 mol CO 2 % yield = . 714 4 . 51 100% = 15 . 8% 004 (part 1 of 1) 6 points Which of the following atoms would be most strongly paramagnetic? 1. Cl 2. Cr correct 3. Ne Su, Yung Final 1 Due: Dec 17 2007, midnight Inst: FAKHREDDINE 2 4. Co 5. S Explanation: 005 (part 1 of 1) 6 points When the equation ?AlCl 3 + ?H 2 SO 4 ?Al 2 (SO 4 ) 3 + ?HCl is balanced, the coefficient of HCl is 1. 6. correct 2. 12. 3. 2. 4. 3. Explanation: A balanced equation must have the same number of each kind of atom on both sides of the equation. We find the number of each kind of atom using equation coefficients and composition stoichiometry. For example, we find there are 6 H atoms on the reactant side: ?H atoms = 3 H 2 SO 4 2 H 1 H 2 SO 4 = 6 H The balanced equation is 2AlCl 3 + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 6HCl and has 2 Al, 6 H, 6 Cl and 12 O atoms on each side. The coefficient of HCl is 6. 006 (part 1 of 1) 6 points Determine the molecular weight of a com- pound given the gas phase data: mass of 27 . 64 g, temperature of 18.4 C, pressure of 956 torr, volume of 14 . 32 L. 1. 36.7 g/mol correct 2. 24.9 g/mol 3. 191 g/mol 4. 0.046 g/mol 5. 279 g/mol Explanation: m = 27 . 64 g V = 14 . 32 L T = 18 . 4 C + 273 . 15 = 291 . 55 K P = 956 torr R = 0 . 08206 L atm mol K Using the ideal gas law, P V = n R T n = P V R T = (956 torr)(14 . 32 L) (0 . 08206 L atm mol K )(291 . 55 K) 1 atm 760 torr = 0 . 752909 mol gas ....
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This note was uploaded on 04/15/2009 for the course CH 54740 taught by Professor Fakhreddine during the Spring '09 term at University of Texas at Austin.

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Final 01 - Su, Yung Final 1 Due: Dec 17 2007, midnight...

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