CHM1045 Lecture 15Outline of Last LectureI. Physical Characteristics of GasesII. Apparatus for Studying the Relationship Between Pressure and Volume of a GasIII. Variation in Gas Volume with Temperature at Constant PressureIV. Charles’s and Gay-Lussac’s LawV. Avogadro’s LawVI. Ideal Gas EquationVII. How Gas Laws WorkOutline of Current LectureI. Density CalculationII. Molar Mass a Gaseous SubstanceIII. Gas StoichiometryIV. Dalton’s Law of Partial PressuresV. Mole fraction (Xi ) = Ni/NrVI. Collecting a Gas over WaterCurrent LectureDensity (d) CalculationsD= m = PM m is the mass of gas in g V RT M is the molar mass of the gasMolar Mass ( M ) of a Gaseous SubstanceM = dRT d is the density of the gas in g/L PExample 1:Calculate the density of carbon dioxide (CO2) in grams per liter (g/L) at 0.990 atm and 55°C.D=PM (.900atm)(44.01g/mol) = 1.62g/L RT (0.0821 L*atm/K*mol)(328K)V= nRT (1mol)(.0821 L*atm/K*mol)(328K) = 27.2 L P .990 atmD= 44.01g/ 27.2L = 1.62 g/LExample 2:A chemist has synthesized a greenish-yellow gaseous compound of chlorine and oxygen and finds that its density is 7.71 g/L at 36°C and 2.88 atm. Calculate the molar mass of the compound and determine its molecular formula.M= dRT = (7.71g/L)(.0821 L*atm/K*mol)(36+273)K2.88atm= 67.9 g/molN=PV/RT = (2.88 atm)(1.00L) (0.0821 L*atm/K*mol)(309K)M= mass/# of moles = 7.71g/.1135 mol = 67.9 g/molGas Stoichiometry Example 3: Calculate the volume of O2 (in liters) required for the complete combustion of 7.64 L of acetylene (C2H2) measured at the same temperature and pressure.Volume of O2 = 7.64 L C2H2 * 5 L O2 2L C2H2= 19.1 LDalton’s Law of Partial PressuresV and T are constantPtotal = P1 + P2 Consider a case in which two gases, A and B, are in a container of volume V.Pa= NaRT Na is the number of moles of A VPB = NBRT nB is the number of moles of B VPT = PA + PB Xa = NaXB= NB Na +NB Na + NBPa = Xa PT = PB = XB PT mole fraction (Xi ) = Ni/NrCollecting a Gas over WaterPT = PO + cPH OPi = Xi PT2KClO3 (s) 2KCl (s) + 3O2
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