GASES

 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,