H10- Gases 2-solutions

H10- Gases 2-solutions - patel (ap28872) – H10: Gases 2...

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Unformatted text preview: patel (ap28872) – H10: Gases 2 – mccord – (51600) 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 12.4 L container at 14.0 ◦ C and 6.84 atm? Correct answer: 115 . 187 g. Explanation: T = 14 . ◦ C + 273 = 287 K P = 6 . 84 atm V = 12 . 4 L m = ? n = P V RT = (6 . 84 atm)(12 . 4 L) ( . 0821 L · atm mol · K ) (287 K) = 3 . 59959 mol O 2 m = (3 . 59959 mol) parenleftbigg 32 g mol parenrightbigg = 115 . 187 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 111 g toluene and 82.0 g benzene. Correct answer: 0 . 534. Explanation: m toluene = 111 g m benzene = 82.0 g n toulene = (111 g toluene) parenleftBig 1 mol 92 . 14 g parenrightBig = 1 . 20 mol n benzene = (82 . 0 g benzene) parenleftBig 1 mol 78 . 11 g parenrightBig = 1 . 05 mol The total number of moles of all species present is 1 . 20 mol + 1 . 05 mol = 2 . 25 mol The mole fraction of toluene is then X toluene = n toluene n total = 1 . 20 mol 2 . 25 mol = 0 . 534 003 (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 70 L of oxygen at 4 . 14 atm and 145 ◦ C with an excess of iron pyrite? Correct answer: 245 . 302 g. Explanation: P = 4 . 14 atm T = 145 ◦ C + 273 = 418 K R = 0 . 08206 L · atm K · mol V = 70 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 = (4 . 14 atm) (70 L) ( . 08206 L · atm K · mol ) (418 K) = 8 . 44871 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 (8 . 44871 mol O 2 ) = 245 . 302 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 7 . 1 L of aqueous solu- tion, what is the molar concentration of the resulting sulfurous acid (H 2 SO 3 ) solution? Correct answer: 0 . 865425 M. patel (ap28872) – H10: Gases 2 – mccord – (51600) 2 Explanation: V = 7 . 1 L SO 2 (g) + H 2 O( ℓ )-→ H 2 SO 3 (aq) . From the stoichiometry, n SO 2 = (8 . 44871 mol) parenleftbigg 8 n SO 2 11 n O 2 parenrightbigg = 6 . 14452 mol ....
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This note was uploaded on 05/12/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas.

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H10- Gases 2-solutions - patel (ap28872) – H10: Gases 2...

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