Exam 1-solutions - Version 155 Exam 1 laude (51635) 1 This...

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Unformatted text preview: Version 155 Exam 1 laude (51635) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. Constants R = 8 . 314 J K 1 mol 1 Definitions Q [C] c [D] d [A] a [B] b G H- TS K w [H + ][OH ] pH - log [H + ] pOH - log [OH ] Equations G = H- T S ln parenleftbigg P 2 P 1 parenrightbigg = H vap R parenleftbigg 1 T 1- 1 T 2 parenrightbigg = MRT T b = iK b m T f = iK f m P i = P i i P = summationdisplay i P i q = mc T q = m H G =- RT ln K K = e G RT ln K 2 K 1 = H R parenleftbigg 1 T 1- 1 T 2 parenrightbigg Q = K [at equil.] [H + ] = ( K a C a ) 1 / 2 [OH ] = ( K b C b ) 1 / 2 [H + ] = K a ( C a /C b ) pH = p K a + log( C b /C a ) [OH ] = K b ( C b /C a ) pOH = p K b + log( C a /C b ) 001 6.0 points Carbon Dioxide 3 1 4 2 A B 200 250 300 350 400 10 10 1 10 2 10 3 10 4 Pressure,bar Temperature, K A sample of carbon dioxide is stored at 10 4 bar and 250 K. This sample is then decompressed to 10 bar at constant temper- ature. Then, at constant pressure it is heated to 400 K. Next, it is compressed at con- stant temperature to 200 bar. According to the phase diagram, how many phase transi- tions has the carbon dioxide gone through, and what is its final state? 1. 2, supercritical fluid correct 2. 2, liquid 3. 2, gas 4. 3, supercritical fluid 5. 3, gas Explanation: Navigate through the diagram through each process. In the first decompression, the solid is decompressed and becomes a liquid and then a gas (2 phase transitions). Upon heating, it becomes a supercritical fluid (no phase transitions). 002 6.0 points What would be the pH of a 0.25 M solution of phenylamine (C 6 H 5 NH 2 ) at room temper- ature? The K b of phenylamine is 4 10 10 . 1. 1 Version 155 Exam 1 laude (51635) 2 2. 9 correct 3. 10.5 4. 13 5. 5 Explanation: [OH ] = (K b C b ) 1 / 2 = (4 10 10 . 25) 1 / 2 = (10 10 ) 1 / 2 = 10 5 pOH =- log[OH ] =- log(10 5 ) = 5 pH = pK w- pOH = 14- 5 = 9 003 6.0 points According to the given phase diagram for carbon dioxide, what are regions 1, 3 and B respectively? Carbon Dioxide 3 1 4 2 A B 200 250 300 350 400 10 10 1 10 2 10 3 10 4 Pressure,bar Temperature, K 1. solid, vapor, critical point correct 2. solid, vapor, triple point 3. liquid, vapor, critical point 4. solid, liquid, triple point 5. solid, liquid, critical point Explanation: As temperature goes up, gas forms. As tem- perature decreases, solid forms. As pressure increases, solid forms. As pressure decreases, gas forms. Point A is the triple point, and Point B is the critical point. 1 = solid, 2 = liquid, 3 = vapor, 4 = supercritical region 004 6.0 points If K w for water at 0 C is 0 . 114 10 14 , what is the pH of water at freezing point?...
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Exam 1-solutions - Version 155 Exam 1 laude (51635) 1 This...

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