CHEM-UA 128 Chapter 10: Atkins CH10
31 May 2016
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Document Summary
Phase transition: conversion of a substance from one phase into another, the key concept to be understood is the concept of equilibrium. At a particular temperature, at a corresponding pressure, a substance undergoes a phase transition. The (e. g. ) solid and liquid phases are in equilibrium. No change in gibb"s free energy- g = 0. Stotal = 0: at a fixed temperature, as long as there is some liquid present, the vapor exerts a characteristic pressure, regardless of the amount of water present. This is the vapor pressure: volatility is determined by the vapor pressure at ordinary temperatures. High vapor pressure at ordinary temperatures, more volatile the substance: molecular model, consider an evacuated, closed container. There is a dynamic equilibrium between the rate of condensation and evaporation: definition: vapor pressure: Ethanol has a higher enthalpy of vaporization than benzene: the gradient of this curve depends on the enthalpy of vaporization.
