CHAPTER 6 NOTES: GASES GAS PRESSURE: The derivation of P = ghd Barometer measures atmospheric pressure – why mercury not water? (0.760 m) (13591.5 kg/m3) (9.80665m/s2) = 101325 N/m2 = 101.325 kPa Manometers: See overlays Natural Simple Gas Laws: Boyles, Charles, Amontons, Avogadros, Gay-Lussac's Ideal Gas Law: PV = nRT Derivation of R and the meaning of an Ideal Gas Molar Volume at STP (O°C and 760 mm) is 22.4 L Applications: n = mass/molar mass AND d = m/V Substitute this into Ideal Gas equation giving PVM = mRT Substiture this into above equation and PM = dRT Note bottom of page 179 on how gas densities differ from liquid densities Hot air balloons and problems associated with Mixtures of gases: Dalton's Law of partial pressures: Total pressure of a mixture of gases is simply the sum of the partial pressures. (Each gas behaves as if it were alone!) Most common application is the collection of gas over water. Pwater + Pgas = Ptotal Equation 6.17 mole fraction = pressure fraction = volume fraction Kinetic Molecular Theory: See overlay for postulates Equation 6.20 describes the root mean square equation. R is in Joules/mol K Diffusion and Effusion.