Unit 12 Gas Laws


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Unformatted text preview: STATES OF MATTER MATTER GASES CHAPTER 13.1 & 14 The Nature of Gases The • • Air – What is it? All gases have similar physical All behaviors. behaviors. • 1 mole of gas = ? L @ STP. • Particles: molecules (diatomic or Particles: polyatomic) or single atoms (noble or inert gases). inert The Physical Properties of Gases of • Have mass (volume-matter). – Density = mass / volume. • • • • • Have compressibility. Fill their container completely. Diffusion: The rate at which gases mix. Exert pressure. Pressure depends on temperature. • Gases have mass. • The distance separating gas particles is The relatively large. relatively • Gases have constant random motion. • Gases exert pressure because of collisions. Gases Collisions are perfectly elastic (no energy of motion is lost). motion • The average KE of the gas is temperature The dependent. dependent. • Gas particles do not exert forces on another. The Kinetic Molecular Theory Theory Measuring Gases Measuring • Liquid / Solid variables: Amount Liquid and Temperature. and • Gases deal with 4 variables: • Amount • Volume • Temperature • Pressure Measuring Gases • • • • • • • Amount (n) “The Mole” Moles to mass to particles n = mass / molar mass Volume (V) Gas fills the container = volume of the Gas container container SI unit is? Measuring Gases • • • • • Temperature (T) Kelvin (vs. Celsius) T(K) = T(OC) + 273 Pressure (P) The result of gas particle collisions The with the walls of the container. with Atmospheric Pressure / Barometer Barometer 1. 2. 3. 4. 5. 6. 7. Pressure exerted by the air in the atmosphere. Result of mass and gravity. Pressure = force / unit area. Force – Newton. Pressure – Pascal (Pa). 1 atm = pressure at sea level. 1 atm = 101.3 kPa = 14.7 lb/in2 = 760 mm Hg (torr). (torr). Atmospheric Pressure / Atmospheric Barometer Barometer 1. Atmospheric pressure vs. altitude / 1. Atmospheric content. content. 2. Barometer: purpose / description. 3. Problems. Enclosed Gases Enclosed • Manometer: purpose / Manometer: description. description. • Problems. The Gas Laws The Mathematical representations Mathematical of the relationships between the four variables (P, V, T, n). four The pressure – volume relationship. • • “Spring of air” or compressibility. At constant temperature, the volume At of a fixed amount of gas will decrease as the pressure increases. decrease • If T is constant, the product of P x V If is a constant value: is PV = K1 PV Boyle’s Law Boyle’s Boyle’s Law Boyle’s • The pressure and volume of a sample of The gas at constant temperature are inversely proportional to each other. proportional P1V1 = P2V2 Sample Problems: Pg. 419 The temperature – volume relationship. Charles’s Law • At constant pressure, the volume of At a fixed amount of gas is directly proportional to its absolute temperature. temperature. • Review absolute zero and the Kelvin Review scale. scale. • V = K2T Charles’s Law Charles’s • The volume of gas is directly The proportional to its temperature. proportional V1T2 = V2T1 Sample Problems: Pg. 421 The pressure – temperature relationship. • At a constant volume , as the pressure At increases the temperature will increase. increases • A directly proportional, linear directly relationship. relationship. Gay-Lussac’s Law P1 / T1 = P2 / T2 Combined Gas Law Combined • No Constants. • V1 x P1 = V2 x P2 T1 T2 Avogadro’s Law The mole – volume relationship. • Equal volumes of gases at the same Equal temperature and pressure contain an equal number of particles. equal • V = K3n • K3 is Avogadro’s Law Constant. is Dalton’s Law of Partial Pressure of • The sum of the partial pressures of The all the components in a gas mixture is equal to the total pressure of the gas mixture. gas • PT = P1 + P2 + P3 + ……. ……. Graham’s Law • Diffusion: the tendency of molecules to move toward areas of low concentration until the concentration is uniform throughout • Effusion: a gas escapes through a tiny hole in its container • Graham’s Law (simple terms): If two objects of two different masses have the same kinetic energy, the lighter object must move faster. Ideal Gas Equation Ideal • An ideal gas is described by the An kinetic-molecular theory postulates. kinetic-molecular • No such ideal gas exists. • Real gases behave like ideal gases Real under many ordinary conditions. under • Exceptions are low temperatures Exceptions and high pressures. and Ideal Gas Equation • PV = nRT R = universal gas constant • Sample problems (pg 427). ...
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This note was uploaded on 01/28/2011 for the course CHEM 101 taught by Professor Petrovich during the Fall '08 term at N.C. State.

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