Exam1Review - Dr. McCord CH302 OVERVIEW for EXAM 1 page 1...

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Textbook Chapters for Exam 1 Chapter 10 sections 9-11. Chapter 16 sections 10 & 11. All of Chapter 17. Background Material You must still have a basic understanding of thermo- dynamics which is Chapters 9 and 10. You should know the interplay between free energy ( G ), en- thalpy ( H ), and entropy ( S ). This is summarized in the equation: G = H - T S (constant T) You should also know what it means to have a spon- taneous process (reaction) and what favors a sponta- neous process. Although you will not be directly tested over Chapters 9 and 10, you will need to have those concepts straight so as to answer thermody- namic questions out of Chapter 17. Physical Equilibria Physical equilibria are those between the different states of matter – solid, liquid, and gas. Every type change has a name: melting solid liquid freezing vaporization liquid gas condensation sublimation solid gas deposition Every change has and energy cost also. All three of the changes above are endothermic as written. The liquid/gas equilibria gets a closer look. Vapor Pressure Be sure you understand what vapor pressure is. Why do we even say vapor? Is there any difference in a vapor and a gas? You can look it up and find lots of criteria for that difference. An easy and useful one is that a vapor is gas state of a substance that is nor- mally a liquid at the given temperature. The vapor pressure of a liquid does increase with temperature, however, it is NOT linear (like ideal gases). The Clausius-Clapeyron equation is just what we need to relate 2 sets of conditions for vapor pressure. The equation is: ln P 2 P 1 = Δ H R 1 T 1 1 T 2 (see p 808) Any pressure units will work here. Only Kelvin tem- perature is valid though. Make sure your H energy units and R units match. Also remember that if the normal boiling point of a substance is given in a problem, you immediately know its vapor pressure at that temperature – it’s 760 torr. Phase Diagrams Now take a pure substance and trap it in a container that you can easily compress (high pressure) and ex- pand (low pressure). You also must be able to control the temperature at any pressure. Now you can test numerous combinations of pressure and temperature and see what’s in the container – solid, liquid, or gas or maybe combinations of them. What comes out of this experiment is a phase diagram. Here is a some- what generic one: Dr. McCord CH302 OVERVIEW for EXAM 1 page 1
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liquid gas P T solid Note where the solid, liquid, and gas phases are. Also note the endpoint of the liquid/gas line - that
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Exam1Review - Dr. McCord CH302 OVERVIEW for EXAM 1 page 1...

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