H10- Gases 2-solutions

# H10- Gases 2-solutions - truitt (wtt255) H10: Gases 2...

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Unformatted text preview: truitt (wtt255) H10: Gases 2 mccord (50970) 1 This print-out should have 22 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 18.9 L container at 38.0 C and 3.06 atm? Correct answer: 72 . 4819 g. Explanation: T = 38 . C + 273 = 311 K P = 3 . 06 atm V = 18 . 9 L m = ? n = P V RT = (3 . 06 atm)(18 . 9 L) ( . 0821 L atm mol K ) (311 K) = 2 . 26506 mol O 2 m = (2 . 26506 mol) parenleftbigg 32 g mol parenrightbigg = 72 . 4819 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 75.5 g toluene and 38.0 g benzene. Correct answer: 0 . 627. Explanation: m toluene = 75.5 g m benzene = 38.0 g n toulene = (75 . 5 g toluene) parenleftBig 1 mol 92 . 14 g parenrightBig = 0 . 819 mol n benzene = (38 . 0 g benzene) parenleftBig 1 mol 78 . 11 g parenrightBig = 0 . 486 mol The total number of moles of all species present is . 819 mol + 0 . 486 mol = 1 . 31 mol The mole fraction of toluene is then X toluene = n toluene n total = . 819 mol 1 . 31 mol = 0 . 627 003 (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 79 L of oxygen at 2 . 07 atm and 146 C with an excess of iron pyrite? Correct answer: 138 . 09 g. Explanation: P = 2 . 07 atm T = 146 C + 273 = 419 K R = 0 . 08206 L atm K mol V = 79 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 . 07 atm) (79 L) ( . 08206 L atm K mol ) (419 K) = 4 . 75611 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 . 75611 mol O 2 ) = 138 . 09 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 2 . 5 L of aqueous solu- tion, what is the molar concentration of the resulting sulfurous acid (H 2 SO 3 ) solution? Correct answer: 1 . 3836 M. truitt (wtt255) H10: Gases 2 mccord (50970) 2 Explanation: V = 2 . 5 L SO 2 (g) + H 2 O( )- H 2 SO 3 (aq) . From the stoichiometry, n SO 2 = (4 . 75611 mol) parenleftbigg 8 n SO 2 11 n O 2 parenrightbigg = 3 . 45899 mol ....
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## This note was uploaded on 02/23/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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H10- Gases 2-solutions - truitt (wtt255) H10: Gases 2...

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