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CHM220 Midterm Study Sheet.docx

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Douglas Mc Intosh

CHM220 Midterm Study Sheet P a g e | 1 1 Definitions  System is the reaction, surroundings is everything else; together is the universe  System: o Open mass and energy exchange o Closed only energy exchange o Isolated no mass nor energy exchange o Diathermic allows energy to leave system as heat o Adiabatic means no heat exchange between system and surroundings  Properties of Matter o Extensive properties values directly proportional to amount of material o Intensive properties values do not depend on amount of material o Intensive properties usually defined as ratio of two extensive properties  State function is path independent  Absolute zero is -273.15C  Boyle’s Law  Charles’ Law  Avogadro’s Law  Ideal Gas Equation  Ideal gas occupies 22.414L at 1atm and 273.15K (STP) o Assuming gas molecules possess negligible volume o No interaction between molecules  Gasses have attracted and repulsive forces o Idea gas only useful for high T and low P  Z= compressibility factor = PV/nRT o Z is 1 for idea gas at any P or T  Van der Waals ( ( )) ( ) o a for attractive intermolecular forces o b for finite volume of molecules o Also unreliable at high P and low T o Slight correlation between a and boiling point 3 Molecules and their Energies  Average kinetic energy for one molecule:  Average kinetic energy for one mole of gas: CHM220 Midterm Study Sheet P a g e | 2  Internal energy is U  EtotE Trans ERot+ EVib EElec  Where N is the number of bonds in the molecule Monoatomic Linear Non-linear Translational Roatational 0 Vibrational 0 ( ) ( ) Total ( ) ( )  ( ) ; so remove T from total internal energy  Quantum Mechanics o Different molecular energy level differences associated with each motion  10 J for electronic -20  10 J for vibrational  10 J for rotational -37  10 J for translational o Easier to promote to higher energy level when difference is smaller o Ratio of populations of molecules in two energy levels given by Boltzmann Distribution: ; N2/N1< 1 o If E is large compared to B T then molecules will crowd to lower energy levels o Energy not quantized for translational motion o Energy is quantized in rotational motion o Most molecules in lower energy level at low temperatures for vibrational motion o Almost all molecules in lower energy levels at low temperatures for electronic motion o So that at room temperature, only translational and rotation motions contribute to U and heat capacity  Heat Capacities o C=U/T = q/T; q is heat required to raise T by T o C =U/T = q /T v V o CP=H/T = q /pT o Heat capacity equations only true for below 300K o CP=a+BT; a and B are constants for given substance o Cp>Cvsince more work is done in constant pressure  Cp-Cv=R o Cp=Cvfor liquids and solids due to small change in volume  Heat capacities of liquids is greater than gases due to weak interactions between molecules CHM220 Midterm Study Sheet P a g e | 3  Energy must be absorbed to break weak intermolecular bonds  Work o w=-PV o More work done in reversible process  Work and heat are not state functions 3.3 First Law of Thermodynamics  Energy can be converte
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