CHEM 1061 1st Edition Lecture 13Outline of Last Lecture I. Molar Mass of a GasII. Partial Pressure of a Gas III. Collecting Gases Over WaterOutline of Current Lecture IV. Stoichiometry with Gas LawsV. Diffusion and EffusionVI. ThermochemistryVII. Heat and WorkVIII. First Law of ThermodynamicsCurrent LectureStoichiometry with Gas LawsUse the gas law quanitites (mol)Ex: 2NaN3(s) 2 Na(s) + 3N2 (g)V = 75.0 LT = 300 KP = 1 atmR = 0.0821How many grams of NaN3 are needed?PV=nRTn=PV/RT=132 gDiffusion and EffusionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Diffusion: movement of gas through another gasEffusion: movement of gas through a vacuumThe rate of effusion inversely proportional to the square root of molar mass.Compare two gases: Rate A/Rate B OR (Square root of Molar Mass B)/(Square root of molar mass A)Real Gases: Used in extreme conditions of low T and high PDeviates from Ideal Gas Las (with Vander Waals Equation)Correction Factors Table 5.4ThermochemistryThermochemistry is heat in chemical and physical changePotential energy: energy due to positionKinetic energy: energy due to motionsystem: part of the universe that we’re focusing on.Surroundings: everything else that is not in the systeminternal energy: (E) Change in E = E(final) – E(initial)Change in E = transfer of E between system and surroundings.Chemical change change in E = E(products) – E(reactants)E(final) < E(initial) change in E < 0Energy is released to surroundings from systemE(final) < E(initial) change in E > 0Energy is absorbed from surroundings from the systemHeat and WorkHeat: (q) energy transferred as a result of difference in temperature between system and surroundingsWork: (w) energy transferred when an object is moved by a forceChange in E = q + wEnergy transferred into system: +Energy transferred out of system: -If only heat: (w=0)change in E = q+w = q+0 = qheat released, q=negative change in E is negativeheat absorbed, q=positive change in E is positiveIf only work (q=0)Change in E = q+w = 0+w = wwork done by a system (final energy is less); w=negativechange in e is negativework done on a system (final energy more); w=positivechange in e is positiveIf both are present you must look at the magnitude to determine EFirst Law of ThermodynamicsEnergy conservation: energy is neither created nor destroyedChange in E(universe) = change in E(system) + change in E(surroundings) =
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