H09- Gas Laws 2-solutions

H09- Gas Laws 2-solutions - marquez(ecm739 – H09 Gas Laws...

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Unformatted text preview: marquez (ecm739) – H09: Gas Laws 2 – McCord – (53110) 1 This print-out should have 17 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 14.7 L container at 22.0 ◦ C and 6.70 atm? Correct answer: 130 . 13 g. Explanation: T = 22 . ◦ C + 273 = 295 K P = 6 . 7 atm V = 14 . 7 L m = ? n = P V RT = (6 . 7 atm)(14 . 7 L) ( . 0821 L · atm mol · K ) (295 K) = 4 . 06656 mol O 2 m = (4 . 06656 mol) parenleftbigg 32 g mol parenrightbigg = 130 . 13 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 86.3 g toluene and 124 g benzene. Correct answer: 0 . 371. Explanation: m toluene = 86.3 g m benzene = 124 g n toulene = (86 . 3 g toluene) parenleftBig 1 mol 92 . 14 g parenrightBig = 0 . 937 mol n benzene = (124 g benzene) parenleftBig 1 mol 78 . 11 g parenrightBig = 1 . 59 mol The total number of moles of all species present is . 937 mol + 1 . 59 mol = 2 . 52 mol The mole fraction of toluene is then X toluene = n toluene n total = . 937 mol 2 . 52 mol = 0 . 371 003 (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 75 L of oxygen at 3 . 36 atm and 160 ◦ C with an excess of iron pyrite? Correct answer: 205 . 917 g. Explanation: P = 3 . 36 atm T = 160 ◦ C + 273 = 433 K R = 0 . 08206 L · atm K · mol V = 75 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 . 36 atm) (75 L) ( . 08206 L · atm K · mol ) (433 K) = 7 . 0922 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 . 0922 mol O 2 ) = 205 . 917 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 3 . 2 L of aqueous solu- tion, what is the molar concentration of the resulting sulfurous acid (H 2 SO 3 ) solution?...
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This note was uploaded on 10/25/2010 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.

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H09- Gas Laws 2-solutions - marquez(ecm739 – H09 Gas Laws...

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