Prof. Marlon Flores Sacedon Kinds of Thermodynamic Process, Internal Energy of an Ideal Gas Heat Capacities of an Ideal Gas Prof. Marlon Flores Sacedon Department of Mathematics and Physics College of Arts and Sciences Visayas State University, Visca Baybay City, Leyte, Phiippines

Kinds of Thermodynamic Process 1. Adiabatic Process (pronounced “ay-dee-ah-bat-ic”) is defined as one with no heat transfer into or out of a system: Q = 0. (adiabatic process) 2. Isochoric Process (pronounced “eye-so-kor-ic”) is a constant-volume process. When the volume of thermodynamic system is constant W=0. (isochoric process) 3. Isobaric Process (pronounced “eye-so-bear-ic”) is a constant –pressure process. (Isobaric process) 4. Isothermal Process (pronounced “eye-so-bear-ic”) is a constant –temperature process. (Isothermal process)

Kinds of Thermodynamic Process

Internal Energy of an Ideal Gas Property of Ideal Gas: The internal energy of an ideal gas depends only on its temperature, and not on its pressure, volume, and its thermodynamic path. It depends only on temperature.

Heat Capacity of an Ideal Gas Molar heat capacity at constant volume (CV) Molar heat capacity at constant pressure (Cp) or (First Law) At constant volume At constant pressure (from First Law) ( from pV=nRT ) (because dQ=dU) Holds for all thermodynamic process Where: Cp = molar specific at constant pressure (J/mol.K) CV = molar specific at constant volume (J/mol.K) R = ideal gas constant ratio of heat capacities (Molar heat capacities of an ideal gas) (ratio of heat capacities)

Molar Heat Capacities of Gases Type of Gas Gas CV (J/mol.K) Cp (J/mol.K) Cp-CV (J/mol.K) (J/mol.K) Monatomic He 12.47 20.78 8.31 1.67 Ar Diatomic H2 20.42 28.74 8.32 1.41 N2 20.76 29.07 1.40 O2 20.85 29.17 CO 29.16 Polyatomic CO2 28.46 36.94 8.48 1.30 SO2 31.39 40.37 8.98 1.29 H2S 25.95 34.60 8.65 1.33

Heat Capacity of an Ideal Gas (average translational kinetic energy of n moles of an ideal gas) (Monatomic, Ideal gas of point particles) (diatomic, Ideal gas of point particles) (polyatomic, Ideal gas of point particles)

Heat Capacity of an Ideal Gas Molar heat capacities for Monatomic ideal gas Molar heat capacities for Diatomic ideal gas Molar heat capacities for Polyatomic ideal gas

Assignment. In an experiment to simulate conditions within an automobile engine, 645J of heat is transferred to 0.185 mol of air-conditioned within a cylinder of volume 40.0cm3. Initially the nitrogen is at a pressure of 3.00x106 Pa and a temperature of 780K. a) If the volume of the cylinder is held fixed, what is the final temperature of the air?. Draw a pV-diagram for this process. b) Find the final temperature of the air if the pressure remains constant. Draw a pV-diagram for this processes.

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