01:160:161 Lecture 2: 01:160:162 Lecture 2: Lecture 2 - 14.5 & 14.6
19 Feb 2016
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Document Summary
Vapor pressure - the pressure of a vapor at an equilibrium with a liquid. Roult"s law: determine the partial vapor pressure of a solution, x is mole fraction, p implies pressure of a pure substance. Strong solute-solute attractiveness leads to a lower vapor pressure than expected, weaker implies lower vapor pressure. Ex) 1 mol of benzene and 1 mol of toluene (pure vap pressure benzene = 760, toluene =290) Vapor pressure = (. 5)(760) + (. 5)(290) = 525. Composition of the vapor is not the same ratio as the combination of the liquid. Composition of vapor is given by partial pressures, Non-volatile solutes have zero vapor pressure - lowers vapor pressure when a non-volatile solute is mixed in a volatile solute. Aqueous solutions have a subzero freezing point and a boiling point over 100oc. Tf = the freezing point depression (in oc) Tb = the boiling point elevation (in oc)
