Gaseous & Liquid State - Chapter 5 Review

Kinetic Theory of Gases

Theory that states:

• Gas particles are in constant motion, moving rapidly & randomly

• Distance between molecules is » than their size so volume is negligible

• No forces of attraction/repulsion between molecules

• Collision between molecules are elastic

• Temperature is the average kinetic energy of each molecule.

Ideal Gases/Real Gases

• Ideal Gases fulfill Kinetic Theory of Gases.

• Noble Gases come close due to their intermolecular forces being very small.

• Real Gases do not follow Kinetic Theory of Gases.

Limitations of Ideal Gas Law

• Real Gases have attraction between molecules

• Real Gases have molecules with non-negligible volumes

Ideal Gas Law at Very High Pressures & Very Low Temperatures

At High Pressure:

• Molecules are VERY close to each other

• Volume of molecules = Volume of Container

• Attraction/Repulsion occurs between molecules

At Low Temp:

• Molecules have no kinetic energy/static

• Molecules condense into a different state

Thus, pressure and volume is lower than expected

General Gas Equation

pV = nRT

• p = Pressure (Pa)

• V = Volume (m³)

• n = # of moles

• R = Gas Constant (8.31 J/kmol)

• T = Temperature (Kelvins)

Vaporization

• Change from liquid to gas state

• Energy transferred makes particles vibrate, weaken the forces of attraction.

• Evaporation: Particles with the most kinetic energy break first at the surface

• Boiling: Forces become weakened enough for all particles to break

Enthalpy Change of Vaporization

• Energy required to change 1 mol of liquid into 1 mol of gas

• O2 (l) → O2 (G) + Energy

Condensation

• Change from gas to liquid

• Particles lose kinetic energy, moving slower

• Increase in forces of attraction

Vapor Pressure

• When the rate of vaporization and condensation equalize within a closed container

• Increases with temperature as gas particles have more energy, causing them to move faster and overcome forces of attraction

• When Vapor Pressure = Atmospheric Pressure is the Boiling Point