Ideal Gas Imaginary Substance Obeys the law of PV=RT At low Pressure and High Temperature – density of gas Decreases Real Gas At High Pressure – Gas start to Deviate from Ideal Gas Measuring of Deviation – Compressibility Factor PV=ZRT Z=PV / RT Z = Vactual / Videal For Ideal Gas Z = 1 For Real Gas Z > 1 Important Laws (Ideal Gas) Boyle's Law (constant temperature) P = constant / V Charles Law (constant pressure) V = constant x T Gay-Lussac’s Law (constant volume) P = constant x T THE ENTHALPY OF ANY SUBSTANCE h=u+pv for an ideal gas h=u+RT h=f(T) dh=du+RdT since R is constant ∆h=∆u+R∆T =Cv∆T+R∆T = (Cv+R)∆T Since h is a function of T only, Cp=(∂h/∂T)p Entropy change of an ideal gas: (Eqn – 1) From the general property relations Q = W+ U Tds=du+pdv And for an ideal gas, du=CvdT, dh=CpdT, and pv=RT, the entropy change between any two states 1 and 2 may be computed as given below ds=du/T+p/Tdv =CvdT/T+Rdv/v S2-s1=Cv ln T2/T1+R ln v2/v1 . Entropy change of an ideal gas: (Eqn -2) Fr