CHEM 1061 1st Edition Lecture 12 Outline of Last Lecture I Temperature II Avogadro s Law III Gas Behavior and Standard Conditions a Standard Temperature and Pressure b Standard Molar Volume IV Ideal Gas Law V Applications of Ideal Gas Law Outline of Current Lecture I Molar Mass of a Gas II Partial Pressure of a Gas III Collecting Gases Over Water Current Lecture Molar Mass of a Gas PV nRT PV mass molar mass RT molar mass mass RT PV Ex Unknown Liquid is in a flask Find the MOLAR MASS P atm P gas 749mmHG V flask 495mL mass 2 56g T 325K 1atm 760mmHG 2 56g x 0 0821 L atm mol K x 325K 68 3072 0 4878 140 038 g mol 0 9855atm x 0 495 L Partial Pressure of Gases These 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 Gases mix completely Assumes no interactions between gases P is proportional to n P total V n total RT P total n total RT V n total n1 n2 n3 etc Mole Fraction X fraction of moles of that gas Ex X a mole fraction A 4 12 0 33 33 Collecting Gases Over Water You need to correct for the vapor pressure of water P gas P H2O P total P gas P total P H2O P H2O found on Table 5 2 and is dependent on temperature EX How many moles of H2 are formed P tube P total 745mmHG V 50 0mL 0 050L T 26 degree C 299K P H2 P total P H2O 745 mmHG 25 2 mmHG amount found on Table 5 2 719 8mmHG 0 947 atm x 0 050 L 299 K x 0 0821 L atm mol K x n H2 n H2 1 93 x 10 3 mol H2
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