Gases

• Fluid that explains to fill the space that contains it.
• Free molecules undergoing breif, elastic collisons.
• Highly compressible,
• Flows from higher to lower pressure,
• Generally act “ideally”.

Pressure

Pressure is described as Force Exerted / Area of affected region. Also commonly know as Newtons / m^2

$ Pressure = \frac{(kg)(s^-2)}{m} $

This unit is called the Pascal (Pa)

• Units
  • IUPAC: Standard Pressure = 100,000 Pa = 1 bar
  • mmHg: millimeters of mercury in a barometer = 1 Torr
  • $ 1 Atm = 760 Torr = 101325 Pa = 101.325 kPa = 1.01325 bar = 14.6959 psi $

The Gas Laws

• The properties of gases were elucidated over many tears by several scientists.
  • Pressure-Volume: Robert Boyle and Robert Hooke
  • Volume-Temperature: J.A.C. Charles
  • Volume-Amount: Amedeo Avogadro
  • Pressure-Temperature: Guiaume Amontons
• $ PV = nRT $ <– Ideal Gas Law

Ideal Gas Law

• Law applies STRICKLY to ideal, non-interacting gases.
• Law applies APPROXIMATELY under condictions where gas molecules interact only weakly.

• Most common gases act like “ideal gases” under typical conditions.

• PV = nRT
  • n is Number of moles.
  • T is temperature in moles.
  • P is pressure
  • V is Volume
  • R is the Gas Constant
    • Equal to about $ 8.31432×10^3 $
• Boyles Law:
  • If n and T are constant:
    • $ PV = (nRT) = C $
    • $ P_1V_1 = P_2V_2 $
• Charles’s Law:
  • Keeping P and n constant:
    • $ V (nR/P)T = CT $
    • $ (V_1/T_1) = (V_2/T_2) $
• Avogadro’s Law:
  • Keep P and T constant:
    • $(V_1/n_1) = (V_2/N_2)$
    • $V = (RT/P)n = Cn$

Using the Ideal Gas Law

Solve for Volume:

• $ V = nRT/P $

Solve for pressure:

• $ P = nRT / V $

Solve for amount:

• $ n = PV/RT $

Gas Constants