PSall - CHEMISTRY 123 Problem Set #1 Phase Equilibria 1 −...

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Unformatted text preview: CHEMISTRY 123 Problem Set #1 Phase Equilibria 1 − 20. Below is the phase diagram for phenol, which has two solid phases, S I and S II , both more dense than the liquid. The transition S I → S II is exothermic. For questions 1 − 6 and 11 − 20 use: (1) vapour or gas (2) liquid (3) solid S I (4) solid S II 1. Which phase is stable in region A? 2. Which phase is stable in region D? 3. Which phases are stable at 61 atm and 64 °C? 4. Which phases are in equilibrium at 2000 atm and 64 °C? 5. Which phases are in equilibrium at 3 × 10 − 3 atm and 40 °C? 6. Which phase is the most dense? 7. Which phase is more dense: B or C? (1) B (2) C 8. The normal boiling point is: (1) 40 °C (2) 64 °C (3) 420 °C (4) none of these 9. The critical temperature is: (1) 40 °C (2) 64 °C (3) 420 °C (4) none of these 10. The transition S I → liquid is exothermic. (1) True (2) False 11. A tube is half filled with solid phenol, then the air is removed and the tube sealed. It is kept at a constant temperature of 35 °C, and the phenol comes to equilibrium. What phases are present in the tube at equilibrium? Page 1 of 6 Identify the phase(s) present in each of the numbered regions on the following graphs. 12 − 16. Isotherm of phenol at 50 °C 17 − 20. Isobaric heating curve for phenol at 1 atm Page 2 of 6 21. A substance has the following properties: boiling point = 75 °C and melting point = –15 °C. Sketch a heating curve for the substance from –50 °C to 100 °C in the diagram shown below. Clearly label the phases present at each individual step (five steps). Time [min] T [K] 373 223 273 22 − 30. For H 2 O, the normal boiling point is 100 °C; the normal melting point is 0 °C; the triple point is at 0.0098 °C and 0.006 atm; the critical point is at 374 °C and 220 atm. Only three phases are present at the temperatures and pressures shown on the graph. T(°C) P(atm) 220 1.0 0.006 0.0 0.0098 100 374 Page 3 of 6 22. Draw the phase diagram for H 2 O using the graph above. 23. Label the regions S (solid), L (liquid), and V (vapor). 24. Circle and label the triple point ( T ), the critical point ( C ), the normal boiling point ( bp ), and the normal melting point ( mp ). 25. At 70 °C, a rigid container is first evacuated, then half filled with water, sealed, and allowed to reach equilibrium. Which phases are present in the end? 26. One of the unique properties of water is the relative density of the solid and liquid phases. Which phase of H 2 O is more dense? 27. On the phase diagram, identify the curve that indicates the relative densities of the liquid and solid phases, and label it with a D . 28. Is the slope of line D positive or negative? Explain in terms of the effect of pressure at constant temperature....
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This note was uploaded on 07/24/2011 for the course CHEM 16 taught by Professor Siao during the Spring '07 term at University of the Philippines Diliman.

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PSall - CHEMISTRY 123 Problem Set #1 Phase Equilibria 1 −...

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