Study Guide for First Test
Study Guide for First Test CHEM 345
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This 6 page Study Guide was uploaded by Kayli Antos on Monday September 21, 2015. The Study Guide belongs to CHEM 345 at Towson University taught by Dr. Ma in Summer 2015. Since its upload, it has received 51 views. For similar materials see Physical Chemistry in Chemistry at Towson University.
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Date Created: 09/21/15
P Chem Test 1 z Introduction Thermodynamic Sustem 0 An open system can exchange energy and matter 0 A closed system can exchange energy but not matter 0 An isolated system cannot exchange energy or matter 0 The boundary between a system and its surroundings can be real or imaginary fixed or movable State of a System 0 Extensive properties are dependent on the mass in a system 0 Intensive properties are independent of mass 0 A combination of properties like mass state temperature pressure and volume make up the physical state of a system z Gas Laws Ideal Gas 0 Molecules have negligible mass and do not interact with each other Real Gas 0 Molecules have mass and interact 0 Can be compressed and have a compression factor Z 0 When Zltl the gas is easy to compress Zgtl means the gas is difficult to compress Condensation of Gases o For ideal gasses at low temperatures pressure and volume are also low 0 At high temperatures pressure and volume are high 0 Real gasses have a critical point which is where liquids and gasses of a substance coexist at the same temperature Only real gasses can be condensed and can be so below the critical point Above the critical point real gasses can be treated as ideal gasses z Kinetic Theory of Gases The Kinetic Model of Gases o Gases are made up of many molecules that are separated by distances that are very great relative to their size 0 Molecules have mass but negligible volume 0 Molecules are in constant random motion 0 Molecules collide with each other and with the walls of the container These collisions are elastic o No attractive or repulsive forces between molecules Molecular Collisions 22 o The average distance that a molecule travels between successful collisions is the mean free path A Equipartition of Enemy Theorem 0 The energy of a molecule is equally divided amongst all its types of motion and degrees of freedom Motions of a Molecule 0 Translational when all atoms move in the same direction Can be along X Y or Z axis 0 Rotation when all atoms move in the same circular path Can be around X Y or Z axis 0 Vibration relative movement of atoms that are not moving in the same direction Does not need to be along the same plane Number of Deqrees of Freedom Type of Motion Monoatomic Linear NonLinear Molecules Molecule Molecule translation 3 3 3 rotation O 2 3 vibration O 3N 5 3N 6 total 3 3N 3N Equipartition of Enerqu For One Mole of Gas 0 For one mole each translational and rotational degree of freedom possesses an energy equal to 1ART Each vibrational degree of freedom possesses an energy equal to RT The First Law Of Thermodynamics Energy cannot be created nor destroyed only converted from one form to anOther AEsystem quotAEsurroundings M5 o The energy transferred into or out of a system due to a temperature difference 0 Heat is positive if it enters the system and negative if it exits 0 Heat Capacity C 0 The measurement of heat energy needed to raise the temperature of an object by 1 degree 0 An extensive property Restricted Thermodynamics o Isobaric constant pressure 0 Isothermal Isothermic constant temperature 0 Isochoric constant volume 0 O Adiabatic no heat transfer Cyclic final stateinitial state Reversible Path o A path in which a process can be reversed at any point by a small change of the variable controlling the process 0 Calorimetry 0 Measurement of changes in heat that accompany chemical reactions 0 Calorimeter 0 3 basic components I Small container made of conductive material which houses the process I Large insulating container for water bath The smaller container is placed in this larger container I Thermometer Must know the heat capacity of the calorimeter Can calculate by knowing the heat given off by a reaction and the change in heat of the reaction in the calorimeter 0 Work w 0 O 0 0 The amount of energy transferred across the boundary between system and surroundings Any energy transfer not dependent on temperature is not heat energy Work is positive if it is done on the system and is negative if the system is doing the work Ideal Gas Isothermal Expansion and Compression Expansion P1 V1 T P2 V2 T I Irreversible Expansion il Process can only go in one direction il Can occur in a vacuum where external pressure is zero and so is work L Also occurs when the external pressure is constant L Work is negative I Reversible Expansion il External pressure equals internal pressure minus an infinitesimal change il Use to find the maximum work a system can do il Work is negative Compression I Irreversible Compression L External pressure is greater than internal pressure I Reversible Compression il Used to find the minimum amount of work the surroundings can do on the system 22 ii T he final volume is smaller than the initial volume and work is positive 0 Reversible Expansion Compression of an Ideal Gas I Must be at a constant temperature Enerqu Internal Enerqu U 0 Total energy of the system Consists of 0 The energies from motion of all molecules translational energy rotational energy and vibrational energy 0 Bond energy angle energy the angle made between 3 atoms as the outer two vibrate and dihedral angle energy between 4 angles arranged into 2 planes 0 Non bonded interactions between atoms more than 5 atoms apart including van der Waals interactions and electrostatic interactions 0 A state function which means that it only depends on the state of the system not the path used to reach the state The change in energy can be calculated by final minus initial Measured in joules SI unit or calories 1 cal 4184 J An extensive property The energy of a system cannot be definitively calculated we can only find the change by A U q w Enthalpy H o Enthalpy cannot be exactly calculated only the change in enthalpy 0 Extensive property 0 Measured in joules OOOO Equations To Know Ideal Gas Equation PV 2 nRT Virial Equation for real gases Z 1 g or B C D are second third fourth virial coefficients van der Waals Equation for ideal gases V nbP nRT nRT a n2 or V nb V2 2 P a V nb nRT a and b are van der Waals parameters with van der Waals Equation for real gases P units of Pa m6 mol2 and m3 mol1 respectively Using molar volume 2 Pressure of a gas with N moles v2 is the mean velocity squared found by squaring the velocity of every molecule and dividing by number of molecules 3RT BMW 2 EKBT ltEtransgt is the average transitional kinetic energy EA of one molecule For real gasses 3 Ms2 The Maxwell Distribution Law 4n ifsze ds dN N is the N ZnRT fraction of molecules moving between speeds s and sds Most probable speed Smp 2 8RT Average speed S n M Root mean square speed vrms xEndzs NAP Collision Frequency Z i ndzg 2 RT NA is Avogadro s Number Mean Free Path A 2 V xEndzN ndZPNA q C T2 T1 q heat C heat capacity constant T1 intial temperature T2 final temperature When C is not constant and is dependent on T dq C dT or or qu fngdT q nf725dT Using molar heat capacity at constant pressure q 11 f7 5P dT Using molar heat capacity at constant volume q n f EVdT Pressure Volume P V Work Expansion Work or or since Pex A dw Pex A dx or Irreversible expansion w f Pede P2 V2 V1 2 Reversible expansion w ff Pede nRT1nV 1 Reversible compression w fIZZ Pede ff PdV nRT1n 1 Reversible expansion compression of ideal gas at constant temperature o Irreversible Reaction is external pressure is constant w Pex V2 V1 0 Infinitesimal change in energy dU dq dw and for P V work V q fvz Pede 0 Energy change at constant value bomb calorimetry A U qv 0 Enthalpy TL 0 Partial pressures P1 2 P x P Where X39 is n1n2 T 2 T 1 the mole fraction of the gas The mole fractions will always add up to 1 P xP P n2 T 1 T 2 n1 1 PV 0 Compress1on factor NRT 0 P NAV Constants to Know R 8314 Jmol K or 008206 L atmmol K z KB Boltzman constant 1381 X 1026 J 22 z NA Avogadoro s Number 6022 X 1023
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