HW07-solutions - arriaga (yga77) HW07 quy (50970) 1 This...

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Unformatted text preview: arriaga (yga77) HW07 quy (50970) 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points What is the mass of oxygen gas in a 10.9 L container at 30.0 C and 4.96 atm? Correct answer: 69 . 546 g. Explanation: T = 30 . C + 273 = 303 K P = 4 . 96 atm V = 10 . 9 L m = ? n = P V RT = (4 . 96 atm)(10 . 9 L) ( . 0821 L atm mol K ) (303 K) = 2 . 17331 mol O 2 m = (2 . 17331 mol) parenleftbigg 32 g mol parenrightbigg = 69 . 546 g O 2 002 10.0 points Toluene (C 6 H 5 CH 3 ) is a liquid compound similar to benzene (C 6 H 6 ). Calculate the mole fraction of toluene in the solution that contains 92.3 g toluene and 37.0 g benzene. Correct answer: 0 . 679. Explanation: m toluene = 92.3 g m benzene = 37.0 g n toulene = (92 . 3 g toluene) parenleftBig 1 mol 92 . 14 g parenrightBig = 1 . 00 mol n benzene = (37 . 0 g benzene) parenleftBig 1 mol 78 . 11 g parenrightBig = 0 . 474 mol The total number of moles of all species present is 1 . 00 mol + 0 . 474 mol = 1 . 48 mol The mole fraction of toluene is then X toluene = n toluene n total = 1 . 00 mol 1 . 48 mol = 0 . 679 003 (part 1 of 4) 10.0 points Iron pyrite (FeS 2 ) is the form in which much of the sulfur exists in coal. In the combustion of coal, oxygen reacts with iron pyrite to produce iron(III) oxide and sulfur dioxide, which is a major source of air pollution and a substantial contributor to acid rain. What mass of Fe 2 O 3 is produced from the reaction is 68 L of oxygen at 2 . 53 atm and 160 C with an excess of iron pyrite? Correct answer: 140 . 579 g. Explanation: P = 2 . 53 atm T = 160 C + 273 = 433 K R = 0 . 08206 L atm K mol V = 68 L MW Fe 2 O 3 = 2(55 . 845 g / mol) + 3(15 . 9994 g / mol) = 159 . 688 g / mol The balanced equation is 4 FeS 2 (s) + 11 O 2 (g)- 2 Fe 2 O 3 (s) + 8 SO 2 (g) Applying the ideal gas law to the O 2 , P V = nRT n = P V RT = (2 . 53 atm) (68 L) ( . 08206 L atm K mol ) (433 K) = 4 . 84184 mol . From stoichiometry and the molar mass of Fe 2 O 3 , m Fe 2 O 3 = (159 . 688 g / mol Fe 2 O 3 ) 2 mol Fe 2 O 3 11 mol O 2 (4 . 84184 mol O 2 ) = 140 . 579 g Fe 2 O 3 . 004 (part 2 of 4) 10.0 points If the sulfur dioxide that is generated above is dissolved to form 4 . 3 L of aqueous solu- tion, what is the molar concentration of the resulting sulfurous acid (H 2 SO 3 ) solution? Correct answer: 0 . 818915 M. arriaga (yga77) HW07 quy (50970) 2 Explanation: V = 4 . 3 L SO 2 (g) + H 2 O( )- H 2 SO 3 (aq) . From the stoichiometry, n SO 2 = (4 . 84184 mol) parenleftbigg 8 n SO 2 11 n O 2 parenrightbigg = 3 . 52133 mol . 3 . 52133 mol of SO 2 will dissolve in 4 . 3 L of water to form a solution that is 3 . 52133 mol 4 . 3 L = 0 . 818915 M in H 2 SO 4 ....
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This note was uploaded on 01/30/2012 for the course CHEM 301 taught by Professor Wandelt during the Spring '08 term at University of Texas at Austin.

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HW07-solutions - arriaga (yga77) HW07 quy (50970) 1 This...

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