01-26-2010 01;07;10PM - Version PREVIEW — Exam 1 —...

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Unformatted text preview: Version PREVIEW — Exam 1 — JOHNSON — (52390) Csteam = 2 Us ' ac (hunter = 4 J/g'ac new, 2 2, 260 J/g AH!“ : 340 J/g 1. -4,000 J 2. 36,600 J 3. -30,000 J 4. -30,300 J 5. —30,600 J correct 6. -8,000 J Explanation: Cooling steam from 115 °C to 100 “C, AH = m-cstmm-AT = 10-2-15 = 300 J. Changing steam to water at 100 0C (the boiling point of water), AH : m - AHm = 10-2, 260 = 22, 600 J. Cooling water at 100 0C to water at 0 CC, AH I m - cm“... - AT = 10 - 4 - 100 = 4,000 J. Changing water to ice at 0 0C (the freezing point of water), AH = 111- AHM 2 10-340 2 3,400 J. Finally, cooling ice from 0 °C to —15 °C, AH = term-AT: 10-2-15 = 300 J. Adding everything together, the Alt-I33,s for the entire process is 30,600 J. LDE Gas Dissolution Theory 003 007 6.0 points Which of the following gases are more soluble in water when their partial pressure above the solution is increased? HI,SO3, NH3, 02, N02, HF, (:12 1. all of them correct 2. Gig, N02, 503, HI 3. N02, 02,HI 4. 303, N02, HI 5. H1, NH3 6. N02, 803 Explanation: Henry‘s Law states that the solubility of gases increase as their partial pressure above the solvent increases. LDE Rank Miscibility in Non—polar 001 008 6.0 points Bank the following liquids in decreasing order of solubility in heptane (C7H15): NH3, CH3OH, CH30H2F, 0014. 1. CH30H2F > 0014 > CH30H > NH3 2. NH3 > CH3OH > CH3CH2F > C014 3. CH30H2F > CH30H > 0014 > NH3 4. COL; > CH3CH2F > CH3OH > NH3 correct 5. CCl4 > CH30H2F > NH3 > CH30H Explanation: ”Like dissolves like.” Heptane is hydrocar- bon, and thus completely non—polar. Car- bon tetrachloride is most soluble since even though the C-Cl bond are polar, there is no net dipole in the molecule, followed by fluo- roethane, which is polar. Methanol is small and very polar (exhibiting hydrogen bond- ing), and ammonia is the most polar of the liquids, and thus least soluble. LDE Simple Raoult’s Law Calc 001 009 6.0 points The vapor pressure of pure acetone (CH3C'OCH3) at 30 ‘C is 240 torr. If salt (NaCl) is dissolved into a sample of acetone until the total vapor pressure of the mixture at 30 0C is 180 torr, what is the mo] fraction of acetone? 1. 0.8 2. 0.2 ...
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