Chp10-411-F2012-Gillan-6slidepage - Chapter 10 Gases 1 2 3 4 5 6 7 8 Characteristics of Gases Gas Pressure and Its Measurement The Gas Laws and Ideal

Chp10-411-F2012-Gillan-6slidepage - Chapter 10 Gases 1 2 3...

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1 Chapter 10: Gases 1. Characteristics of Gases 2. Gas Pressure and Its Measurement 3. The Gas Laws and Ideal Gas Law 4. Gas Law Applications 5. Gas Mixtures 6. Kinetic-Molecular Theory 7. Effusion and Diffusion 8. Non-Ideal Gases CH 4 2 1. Some Key Gas Properties A gas is a physical state of an element or compound. Contrast with liquid or solid states of matter (see Chp. 1): gases expand to fill the entire container they are placed in. - move rapidly around container & exert force on its walls. gases have low densities (<< moles/cm 3 vs. liquids). - thus they are easily compressed into smaller volumes. gases (ideally) interact weakly with other gases and often are highly miscible (forming homogeneous gas mixtures). 3 2. Gases and their Pressure Properties Elemental gases : He, Ne, Ar, Kr, Xe and H 2 , O 2 , N 2 , F 2 , Cl 2 Selected common molecular gases : CH 4 , NO 2 , NO, N 2 O, CO, CO 2 , NH 3 , HCl, H 2 O Air (mixture) 78% N 2 , 21% O 2 , 1% Ar P=F/A 2009 Hail Storm more force (ma) = 1 atm 4 Gas Pressure (P) Defined Pressure Units: area on accelerati mass area force pressure Pa 1 pascal 1 s m kg m ) s / m ( kg 2 2 2 1.013 × 10 5 Pa = 101.3 kPa = 1.013 bar = 14.7 lb/in 2 = 1 atm = 760 mm Hg = 760 torr SI derived unit Example: If you inflate your car’s tires to 27.5 lb/in 2 , what is this in torr and atm? Ans : torr 1 2 14 lb/in 14.7 torr 760 lb/in 27.5 2 2 (or 1.87 atm) 5 Mercury (Hg) to Measure Pressure Barometer invented by Torr icelli (17 th century) air pressure on Hg pool = mm Hg Manometer P gas = 760 + 32.6 torr (no gas) 6 Manometers – Gas Pressures P gas = P atm P gas < P atm P gas = P atm - h P gas > P atm P gas = P atm + h open-end manometers when P gas = 0 torr (mmHg) then h = P atm = 760 mm Note : 0 torr = no gas molecules = a vacuum!