CH 302 1st Edition Lecture 2 Outline of Last Lecture I. EnthalpyII. EntropyIII. Gibb’s Free EnergyOutline of Current Lecture I. Quick RemindersII. Vapor PressureIII. Phase diagramCurrent LectureQuick Reminders:- Delta H of vaporization is always positive- What would happen if there were no IMFs?o There would be no attraction between molecules and they would all wander away and spread out all over the universeo This is why IMFs are important- Temperature is related to Kinetic energy! (KE = ½ mv^2)- Therefore when temperature increases, kinetic energy increasesVapor Pressure:You have two containers. One has a total volume of 2 L and the other has a total volume of 1 L. Into each container, you place 500 mL of liquid ether. They have the same temperature. Which container has a higher pressure at equilibrium?- They are exactly the same because the pressure is the same if it is the same liquid and same temperatureWhich container has the greater number of molecules in the gas phase?- The 2 L container*The relationship between Vapor Pressure and delta H of vaporization is inversely proportional (As VP increases, DH decreases)- The temperature at which the vapor pressure equals the external pressure is the boiling temperature- Vapor pressure is dependent on T- Vapor pressure is independent of the amount of liquid present- The stronger the IMFs, the bigger the difference between the liquid and the gas, the larger the DH and the lower the VPWhy does octane have a lower vapor pressure than hexane?- Octane has stronger intermolecular forcesPhase Diagram:- Normal phase changes occur at 1 atm, butphase change temperatures vary withpressure- Phase changes are an equilibriumcondition- You can refer to a phase diagram todetermine at what phase a particularsubstance will be in based on the externalpressure and
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