DP Study Guide for Chapter 11

DP Study Guide for Chapter 11 - DP's Study Guide for...

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DP’s Study Guide for Chapter 11. General Chemistry, 4th Ed.”, Hill, Petrucci, McCreary, and Perry (ISBN 0-13-140313-3) In Chapter 11 we study phase changes and how intermolecular forces are part of that process. 1.1 Kinetic Molecular Theory of Gases is extended to the liquid and solid phase. The molecules in a liquid are closer together than a gas and are attracted to each other by intermolecular forces the magnitude of which depends upon the molecule. In solids the molecules are closer still moving much less. To go from one phase to another an energy change is needed. Most folks associate phase changes with temperature. This is true, but a limited view of what really goes on because we only operate at a single pressure. This “phase change” energy is required no matter what the temperature, and is roughly independent of temperature. Some Enthalpies of Vaporization at 298 K are listed in Table 11.1. At 0 C o , solid water (aka ice), liquid water, and water vapor (do not say steam) can all exist together Learn: the terms melting (fusion), freezing, vaporization, condensation, sublimation, and deposition. Be able to work problems associated with each change: Problems: 17, 21, 32, 37. If you are changing the temperature of a single phase, solid, liquid, or gas, the energy needed is determined by the heat capacity of the stuff in that particular phase. See Chapter 6.5 where you can get the rink dink formula ∆H = ms∆T. In this chapter energies need to change phase and temperature are considered together. Sometimes such transitions are diagramed in heating or cooling curves. 11.2 Vaporization and Vapor pressure. Molecules in a liquid are not stationary but move around. According to the KMT, some of these molecules have enough energy to escape the liquid, ie defeating the intermolecular forces. After escaping the molecules of liquid strike the air above this produces something called vapor pressure. Some of the molecules leave the area of the liquid completely others loose enough energy and return to the liquid. This leaving and returning process is called dynamic equilibrium, molecules enter and leave the liquid at the same rate giving the appearance that nothing is going on. A version of the idea gas law equation can be used to calculate vapor pressures and vapor volumes: Problems 27, 29, 31, As the temperature rises the average KE of the molecules increases and more leave the liquid increasing vapor pressure vapor pressure increases with temperature. The temperature at which the vapor pressure of the liquid equals the pressure of gas over the liquid is called the boiling point. Of course if you take some of the air over the liquid away, the liquid will boil at a lower temperature. Conversely, if air pressure is added, the
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This test prep was uploaded on 04/16/2008 for the course CHEM 1123 taught by Professor Paul during the Fall '06 term at Arkansas.

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DP Study Guide for Chapter 11 - DP's Study Guide for...

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