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Quiz 2-solutions - Version 047 Quiz 2 fakhreddine(51650...

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Version 047 – Quiz 2 – fakhreddine – (51650) 1 This print-out should have 4 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 3.0points A solution prepared by adding 0 . 23 g of a polymer to 0 . 6 L of toluene (methylbenzene, a common solvent) showed an osmotic pressure of 0 . 838 Torr at 24 C. What is the molar mass of the polymer? 1. 46616.7 2. 18390.4 3. 17184.6 4. 5776.21 5. 8860.9 6. 24870.5 7. 8472.94 8. 12631.7 9. 54614.9 10. 23058.2 Correct answer: 8472 . 94 g / mol. Explanation: m = 0 . 23 g V = 0 . 6 L T = 24 C + 273 = 297 K P = 0 . 838 Torr R = 0 . 08206 L · atm K · mol We assume the polymer to be a non elec- trolyte, so i = 1, and Π = iRT M 1 M = V MW x m = iRT P MW x = iRT m P V = 1 (0 . 08206 L · atm K · mol ) (297 K) (0 . 23 g) (0 . 838 Torr) (0 . 6 L) × 760 Torr 1 atm = 8472 . 94 g / mol . 002 2.0points Write the equilibrium expression for the fol- lowing reaction: 2 NO ( aq ) + 4 H 2 O( ) ←→ 3 H 2 ( aq ) + 2 H + ( aq ) + 2 NO 3 ( aq ) 1. K = [ NO ] 2 [ H + ] 2 · [ NO 3 ] 2 2. K = [[ H + ] 2 · [ NO 3 ] 2 [ NO ] 2 3. K = [ H 2 ] 3 · [ H + ] 2 · [ NO 3 ] 2 [ NO ] 2 · [ H 2 O ] 4 4. K = [ NO ] 2 [ H 2 ] 3 · [ H + ] 2 · [ NO 3 ] 2 5. K = [ H 2 ] 3 · [ H + ] 2 · [ NO 3
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