IDEAL GAS: attractive forces between molecules are assumed negligible, but they can interact through collisions.
Pressure of gas on container is due to collisions of gas molecules against container walls. IDEAL GAS LAW where n = number of moles of gas molecules R = Universal Gas Constant = 8.32 J/(mol.K) T = Absolute Temperature (K) P = Absolute (or Total) Pressure Note: T(K) = T (C) + 273.15 SPECIAL CASES Often some variable is fixed and the Ideal Gas equation can be simplified. • CONSTANT TEMPERATURE PROCESSES (ISOTHERMAL): BOYLE’S LAW For ISOTHERMAL PROCESSES: So if n is also constant: Implication: If an Ideal Gas, initially in state 1, is changed by an isothermal process to state 2, the two states are related by
E.g.: 1000 mL of ideal gas is placed into a container that could expand or contract at 1 atm. What happens to the volume when the gas is subjected to 2 atm of pressure?
Clinical application: Venting of IV bottles
Physiological application: Role of the chest cavity in inflating the lungs. When the diaphragm and respiratory muscles contract, the thoracic cavity volume increases, thereby reducing cavity pressure to a value below atmospheric pressure. This causes air to flow into the lungs.
• CONSTANT PRESSURE PROCESSES (ISOBARIC): CHARLES' LAW
For ISOBARIC PROCESSES In enclosed system n is also constant, In other words,