Inquiry 4: Gas Laws

What are some properties of gases?

• Flow density

• Free flowing/forming

• Compressible and Expandable

• Large spaces between molecules

• Volume changes with temperature (expands when heated)

• Diffusive - form homogeneous mixtures

Kinetic Molecule Theory

• Particles travel in straight lines

• Gas particles constantly collide elastically

• Gas particles are small and volume is relative to container

• Negligible interactive forces between gas particles

• temperature dictates kinetic energy of gas molecules

Pressure measurements

• 1 atm (atmosphere) = 1.01325 × 10^5 Pa = 101.325 kPa

• Torr - 1/760 atm = 101.325/760 kPa = 133.322 Pa

• Bar = 1 × 10² = 1 × 10^5 Pa

• Particle pressure:

  • P (total) = P(gas 1) +P (gas 2) + P(gas 3) + etc

Molar Volume

• 1 mole of gas = 22.71L at 0 degrees Celsius (273.15 Kelvin) at 100 kPa (Standard Pressure)

• 1 mole of gas = 24.79L at 25 degrees Celsius (298.15 Kelvin) at 100 kPa (Standard Pressure)

• This is constant for all ideal gases

Ideal Gas Law

• PV = nRT

  • P = pressure (kilopascals - kPa)

  • V = volume (litres - L)

  • n = moles (mol)

  • R = gas constant (8.314 J mol/K)

  • T = temperature (kelvin - K)

Boyle’s Law

• Deals with pressure and volume

• As volume increases, pressure decreases

• As pressure increases, volume decreases

• P1V1 = P2V2

Charles’s Law

• Deals with volume and temperature

• As volume increases, temperature increases

• As temperature increases, the volume increases

• V1/T1 = V2/T2

Gay-Lussac’s Law

• Deals with pressure and temperatures

• As pressure increases, temperature increases

• As temperature increases, pressure increases

• P1/T1 = P2/T2

Avogadro’s Law

• All gases at the same temperature and pressure must have the same amount of moles

• If the amount of moles increase, volume will increase

• V = kn

• V1/n1 = V2/n2

Combined Gas Law

P1V1/T1 = P2V2/T2