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CHEM 433 - 9/16/11 II. Gases —> Intro and definitions. (1.1) A. Ideal Gases —> The ideal gas Law (1.2) —> “Equations of “State” —> Using the Ideal Gas Law —> Dalton’s Law: Mixtures READ: Chapter #1 HW: HW #2 via email
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Gas: A form of matter that fills any container. Features : - Molecules in “ceaseless random motion”. - Speeds increase with temperature. - Molecules widely separated except during collision. - Paths “largely unaffected” by IMF. (IDEAL = NO IMF) Physical State: The “condition” of the system as specified by its physical properties. The State of a pure gas is specified by p, V, T, and n. Equation of State: An Equation that relates p,V,T (e.g. p = f(n,V,T)). Perfect (or Ideal) Gas: Obeys: pV=nRT or (p=nRT/V) Pressure: Force/Area. SI Unit: Pascal (Pa) = N/m 2. http://en.wikipedia.org/wiki/Pressure_measurement http://en.wikipedia.org/wiki/Pressure_measurement Others: Atmospheres (atm), bar, & Torr (=mmHg). (1 atm = 760 Torr = 1.01325 bar = 1.01325 x 10 5 Pa).
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Standard Pressure: 1 bar (p°) Mechanical Equilibrium: Equal pressures (e.g. 2 gases separated by a movable piston). Temperature: A property that indicates the direction of heat flow. Thermal Equilibrium: Temperatures are equal (no heat flow). Thermodynamic Temperature Scale: T(K) = Q(°C) + 273.15 0th Law of Thermodynamics: If A ~ B, and B ~ C —> A ~ C (~ = in Thermal EQ w/) Diathermic Boundary: Change of state can occur upon contact (heat transfer allowed). Adiabatic Boundary: No change of State occurs upon contact (no heat transfer).
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The unofficial mascot of CHEM 433: The frictionless movable piston F.M.P.
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Boyle’s Law: PV = const. or: p = 1 / V (constant T,n)
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Charles’ Law(s) : P ~ T V ~ T (constant n, and p or V)
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Avagadro’s Principle: V ~ n (constant T, p)
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What is the volume of 1 mol of gas at: a)STP (T=0°C and p = 1 atm) ? b)SATP (T=298.15K, p=1 bar)? a)22.4 L b)24.8 L
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Using the Combined Gas Law: Calculate the final temperature when 1 mol of gas a SATP is compressed from 24.8 To 12.4 L and the pressure increases from 1.0 to 2.0 bar? THE SAME - about 298K
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Using Dalton’s Law: Calculate P N2, P O2 and P Ar in the atmosphere, assume P TOT = 1.00 atm. moles P N2 = 0.78 atm, P O2 = 0.21 atm, P Ar = 0.0093 atm
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