HW 10 - johnson(mjj622 – H10 Gases 2 – mccord –(50970...

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Unformatted text preview: johnson (mjj622) – 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 17.8 L container at 37.0 ◦ C and 8.10 atm? Correct answer: 181 . 28 g. Explanation: T = 37 . ◦ C + 273 = 310 K P = 8 . 1 atm V = 17 . 8 L m = ? n = P V RT = (8 . 1 atm)(17 . 8 L) ( . 0821 L · atm mol · K ) (310 K) = 5 . 665 mol O 2 m = (5 . 665 mol) parenleftbigg 32 g mol parenrightbigg = 181 . 28 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 50.8 g toluene and 105 g benzene. Correct answer: 0 . 291. Explanation: m toluene = 50.8 g m benzene = 105 g n toulene = (50 . 8 g toluene) parenleftBig 1 mol 92 . 14 g parenrightBig = 0 . 551 mol n benzene = (105 g benzene) parenleftBig 1 mol 78 . 11 g parenrightBig = 1 . 34 mol The total number of moles of all species present is . 551 mol + 1 . 34 mol = 1 . 90 mol The mole fraction of toluene is then X toluene = n toluene n total = . 551 mol 1 . 90 mol = 0 . 291 003 (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 78 L of oxygen at 3 . 37 atm and 151 ◦ C with an excess of iron pyrite? Correct answer: 219 . 35 g. Explanation: P = 3 . 37 atm T = 151 ◦ C + 273 = 424 K R = 0 . 08206 L · atm K · mol V = 78 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 = (3 . 37 atm) (78 L) ( . 08206 L · atm K · mol ) (424 K) = 7 . 55487 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 (7 . 55487 mol O 2 ) = 219 . 35 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 . 773867 M. johnson (mjj622) – H10: Gases 2 – mccord – (50970) 2 Explanation: V = 7 . 1 L SO 2 (g) + H 2 O( ℓ )-→ H 2 SO 3 (aq) . From the stoichiometry, n SO 2 = (7 . 55487 mol) parenleftbigg 8 n SO 2 11 n O 2 parenrightbigg = 5 . 49445 mol ....
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HW 10 - johnson(mjj622 – H10 Gases 2 – mccord –(50970...

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