Determining the molecular mass of a gas

Determining the molecular mass of a gas - Christina Wong AP...

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Christina Wong AP Chemistry 4 th hour 3/31/2010 Determining the Molecular Mass of a Gas I. Purpose The purpose of this lab was to determine the molecular mass of a substance from measurements of the density of its vapor. II. Observations and Data Mass of flask + cap 83.96 g Mass of flask + cap + condensate 84.34 g Volume of flask (V 1 ) 125 mL Temperature of water, (T 1 ) 98 C = 371 K Barometric pressure 29.98 inHg = 761.5 mmHg III. Calculations 1. Find the mass of the condensed vapor: Mass = part b – part a Mass = 84.34 – 83.96 = 0.38 g 2. Find the volume of the vapor at STP: V 2 =V 1 x P 1 x T 2 /P 2 x T 1 V 2 =125mL x 761.5 mmHg x 273 K / 760 mmHg x 371 K V 2 = 92.16 mL 3. Find the molecular mass of the gas sample Molecular mass = m (g) x 22.4 (L/mole) / V 2 (L) Molecular mass = 0.38 g x 22.4 L/mole / 0.09216 L Molecular mass = 92.36 g IV. Conclusions and Questions 1. Using the molecular formula supplied by the teacher, calculate the actual molecular mass of the unidentified substance. The actual molecular mass of ethanol (C
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Determining the molecular mass of a gas - Christina Wong AP...

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