# Chemistry Thermodynamics

 Heat (>, <, or = 0?) If q>0, then heat is added to the systemIf q<0, then heat is removed from the systemIf q=0, then dU=w Work (> or < 0?) If w>0, work is being done on the system.If w<0, work is being done by the system. Internal Energy (dU) --> Any Conditions dU = q + wdU = ncv(dT) Heat --> General (Any Conditions) q = c(dT) Enthalpy Change --> Any Conditions dH = dU + d(PV)dH = ncp(dT) Work Against a Constant External Pressure w = -Pext(dV) Reversible, Isothermal Work w = -nRTln(V2/V1) Work at Constant Volume w = 0 Relate cp and cv cp = cv + R Heat at Constant Volume q = ncv(dT)Note: This also equals dU, because at constant volume, w=0. Heat at Constant Pressure q = ncp(dT)Note: This also equals dH Enthalpy A state function that represents the heat transferred for a system under constant pressure (qp)dH = dU + d(PV)For an ideal monatomic gas, this can be rewritten as: dH = dU + d(nRT)dH = qp = ncp(dT) Molar Heat Capacities for Ideal, Monatomic Gases at Constant V and Constant P cv = (3/2)Rcp = (5/2)R Boltzman's Equation S = KBln(omega)KB = 1.38 x 10-23 J/K Entropy Change for Reversible, Isothermal Expansion dS = nRln(V2/V1)dS = qrev/T Entropy Change at Constant Pressure dS = ncpln(T2/T1) Entropy Change at Constant Volume dS = ncvln(T2/T1) Entropy Change for Phase Changes dS = (dHPT)/T dSuniverse and Spontaneity If dSuniv > 0, the process is spontaneous as writtenIf dSuniv < 0, the process is spontaneous in the reverse directionIf dSuniv = 0, the process is at equilibrium Gibbs Free Energy dG = dH - TdS AuthorAnonymous ID74132 Card SetChemistry Thermodynamics DescriptionExam 2 Stuff Updated2011-03-21T04:53:28Z Show Answers