Exam 1-solutions - Version 026 Exam 1 sutcliffe (51045) 1...

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Unformatted text preview: Version 026 Exam 1 sutcliffe (51045) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Consider the reaction 2 Fe 2 O 3 (s) + 3 C(s) 4 Fe(s) + 3 CO 2 (g) H = 462 kJ / mol S = 558 J / molK Calculate the equilibrium constant for this reaction at 525 C. 1. 8 . 15 10 2 correct 2. 1 . 51 10 17 3. 3 . 04 10 3 4. 1 . 9 10 6 5. 1 . 23 10 1 6. 2 . 18 10 2 Explanation: G = 462000- (798 . 15 K) (558) = +16632 . 3 J K = e G/ ( R T ) = e 2 . 5064 = 8 . 1558 10 2 002 10.0 points Water vapor condensing to liquid water is what type of process? 1. exothermic correct 2. endothermic 3. isotopic 4. enthalpic Explanation: 003 10.0 points What is the Tyndall effect? 1. the ability to scatter light correct 2. the ability to exist as a rainbow of colors 3. the ability to make fog 4. the ability to form a gel Explanation: A characteristic property of colloids, their ability to scatter light, is called the Tyndall effect. 004 10.0 points The phase diagram for a pure substance is given below. Solid Liquid Vapor 50 100 150 200 250 300 100 200 300 400 Temperature, K Pressure,atm The solid sublimes 1. if warmed at any pressure below 50 atm. correct 2. at 300 K and 100 atm. 3. at 200 K and 100 atm. 4. at 400 K and 200 atm. 5. at 300 K and 75 atm. Explanation: 005 10.0 points The vaporization of water from the liquid Version 026 Exam 1 sutcliffe (51045) 2 state would involve the destruction of in- termolecular hydrogen bonds between water molecules but would still leave each water molecule intact. 1. False 2. True correct Explanation: H 2 O hydrogen bonds with neighboring wa- ter molecules. These bonds must be overcome for a molecule to escape liquid phase and be- come vapor. H 2 O molecules must remain intact. Phase changes are physical changes, not chemical changes. 006 10.0 points If the reaction quotient Q for some hypothet- ical reaction is 100, how does G compare to G ? 1. G > G correct 2. G = G 3. G < G 4. There is insufficient information given to determine the answer. Explanation: G = G + RT ln Q If Q = 100, then the natural log term will be positive. This means that the non standard value of G will be bigger (more positive) than the value of G . 007 10.0 points The partial pressure of CO 2 in the atmosphere is 3 . 9 10 4 atm. When drinking soda is put in a can, assume that there is 2.0 atm CO 2 in the 2.0 mL gas space above the soda. (The actual CO 2 pressure varies with type of soda.) What is the approximate ratio of the molar concentrations of CO 2 (aq) in the soda before it is opened to that in the soda after it has been opened and reached equilibrium with the surrounding atmosphere; i.e. , has gone flat? 1. 5 10 3 correct 2. 2 10 4 3. 2 10 2 4. You need Raults Law constant for CO...
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Exam 1-solutions - Version 026 Exam 1 sutcliffe (51045) 1...

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