# Physical chemistry Test 1

 Work Formula F*dl Work Units kg m^2/s^2 Kinetic Energy .5 mu^2 Relatino betwene work and energy w = E_kf-E_ki Kinetic Energy Energy posessed by a body by virtue of being in mostion Potential ENergy Energy posessed by a body by virtue of position System A specific segmentof hte world with deffinite boundaries on which we focus our attention Surroundings The part of the world immediately surrounding a system Universe System and its surroundings Open system Can transfer heat and material Closed system Can only transfer heat Isolated system Can transfer neither heat nor matter Intensive property Not a function of quantity Extensive propety Directly a function of quantity Equation of state An equation that describes the condition of a system as a function of intensive properties Equilibrium The systems variables of state are not changing with respect to time Heat The kinetic energy of molecualr motion Zeroeth law of thermodynamics If A and B are in thermal equilibriumAnd B and C are in thermal EquilibriumThen A and C are in thermal Equilibrium Boyles Law Applies under Isothermic Conditrions. If temperature and nubmer of mols are held constant then PV=Constant Isotherm Temperature is held constant Isobaric Pressure is held constant Gay-Lussacks Law If Pressure and mols are fixed then V/T =Constant m is? mass M is? Molar Mass Ideal Gas Law PV=nRT 3 Assumptions of ideal gas law 1) gas is assumed to be composed of individual particles whose actual dimensions are small in comparison to the distance between them.2) These particles are in constant motion and therefore have kinetic energy.3) Neither attractive nor repulsive forces exist between the particles. N Number of molecules present Pressure in terms of mean square speed P= Average Kinetic Energy of a molecule in a system e=. Partial Pressure Pressure exerted by a single component of a gas mixture. Defined by molar fraction* pressure total Grahms law of Effucsion R Collision frequency How many collisions pe second does a molecule experieince units : 1/s Collision Density How many colisions per unit of second per volume occur? Mean free path How far a molecule travels before a collisiondistnace ump Most probable velocity. Peak of maxwell curve z Compression factor= z>1 Repulsive forces dominate (b term from nonideal gas) Z<1 Attractive forces dominate (a term) Van Der Waals equation Uses a to account for attraction and b to account for repulsion Adiabatic No change in Heat (Q) Terms in the maxwell constant of dN/Ndu Normalization factor: Boltzman distribution: Incremental volume: Boltzman distribution )Maps likely distribution of particle velocities Incremental volume 4\ Accoutns for incremental volume in maxwell distribution sphere Maxwell normalization factor NOrmalizes maxwell distribution by total molecules likely to be present  Average speed of a molecule in system given by maxwell normalization factor. Actually less common than Formula:  Least common of the important speeds in maxwell distribution, this is the root mean square speed. Average kinetic energy per molecule formula and function of e= =.5mu2This is a function primarilly of temperature. When u is not velocity, what is it? (fucking headache) Internal energy: the internal energy of a molecule is the sum of its heat and worku=q+w First law of thermodynamics Energy can neither be created nor destroyed. Only moved. What are the Five macroscopic properties Pressure, Temperature, Volume, Mass, Enegy What are state functions? The macroscopic properties that define a substance What happens if we fix 3 of the state functions The other two are then known What is path dependence? A path dependent function is dependent on how one reaches a point. Using a mountain analogy: Height to reach a point is always constant, distance is a function of the route you take to reach tehat point. Are state functions path dependent? No. They are not. It is part of what makes them state functions. Equilibrium states Points at which without an external operator acting, a system will hold in a steady state over time. 3 Criteria for equilibrium state The mechanical properties, chemical properties and temperature throughout a system must be uniform for something to be in an equilibrium state Reversible vs Irreversible processes If a system is changed slowly enough to maintain an equilibrium state, it is considered a reversible process. Sign convention for heat (q) If a system absorbs heat, q is positive. If a system loses heat, q is negative Sign convention for work on a system (w) If work is done on a system (work flows in), then w is positiveIf work is done by a system (work flows out), then w is negative. q Heat of system. function ot work and internal energyq= What can we know about internal energy of a system over an operation Its change. We do not know how much internal energy a system posesses, only how much it changes over time What type of properties are heat and work Path properties. They are dependent entirely on path and not functions of state. they are inexact integrals. Nature of intenral energy (u): What are the 3 things that contribute 1) kinetic energy of motion of hte individual molecules2) Potential eneryg that arise form interactions between molecules3) Kinetic and potential energy of nuclei and elctorns with inthe individual molecules. What are the four types of work Chemical: energy of breaking chemical bondsElctrical: Work performed by currentMechanical : Gross work of physical motion of massesOsmotic: Transportation and concentration of chemicals What is work defined as? A force over distance. IE ENERGY How do we define reversible work in thermodynamics? (Form and two notes) wrev=-\ Note that if P is not constant, we must deffine it as a function of volume before doing this calculation.Note that dv implies an infintessimal volume change. Is more work done through reversible or irreversible processes? What do graphs look like? If a process is reversible, it requires more work to do because pressure is assumed constant constant and graph of change is curved.If a process is irreversible, then less work is required as both pressure and volume are assuemd to change. Graph is straight drop of pressure and the straight change of volume. Which type of process(Reversible or irreversible ) generates more heat? Why? We assume inc U to be constant. With this as a given and the realization that there will be more heat generated by irreversible work because there is less actual work done. What is formula and assumption of irreversible work? Irreversible work is assumed to happen suddenly. Too suddenly to be considered incremental. As such, we use the final pressure to calcualtewirr=-P2(Vfinal-Vinitial) When is work maximized? When a process is reversible. What happens to internal energy for an isochoric process? It is only a function of change of heat as volume is 'fixed' Isochoric Constant volume What is Enthalpy (H)? Enthalpy is a state function equal to :H= U + PV = internal energy + PRessure * VolumeThis deffinition is only valid if all work is PV work. What is the change in heat (q)for a constant pressure system? inc Endothermic process definition One in which q and w are positive.This implies that heat and work flow into system. This also implies that the surroundings will lose heat and feel colder. Exothermic Process One in which q and w are negative.This implies that heat and work flow out of the system. This also implies that the surroundings will gain heat and feel hotter in temperature. What are the two forms of heat capacity and why do we have them? Isochoric: Constant VolumeIsobaric: Constant Pressure Heat capacity is not a state function. It fluctuates fased on sate functions and as suc hwe need to account for environmental conditions. What should we know about Cv and what is its formula? This is isochoric heat capacity. It implies that there is a constant volume in system. In general, it is less like lab work/real systems.Due to the lack of change in volume, we asusme this to be purely a function of intenral energyIts formula is: Cv= What should we know about CP and what is its formula? This is Isobaric heat capacity. While pressure is constant, volume may vary and we thus may need to account for work. As such it is a function of Enthalpy (H) and is far more common in the lab.Cp = \gr What is heat capacity? How much heat energy (Joules) a kilogram of a substance must absorb to increase by 1 K in temperature. It varies with temperature and type of system. How are Isochoric and Isobaric heat capacity related? Cpm =Cvm +R When can you use either form of heat capacity to find change in heat? When working with an ideal gas, either form of heat capacity is equally valid. What is formula for change in enthalphy? i What is formula for change in internal energy? in AuthorAnonymous ID132812 Card SetPhysical chemistry Test 1 DescriptionPhysical chemistry test 1 Updated2012-02-04T21:09:37Z Show Answers