1e03-tut1-a

# 1e03-tut1-a - CHEM 1E03 TUTORIAL#1 solutions 1 A sample of...

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CHEM 1E03 TUTORIAL #1 solutions ________________________________________________________________________ Page 1 of 4 1. A sample of a noble gas has a mass of 0.102 g and exerts a pressure of 0.242 atm in a 0.260 L vessel at 27 o C. Is the gas He, Ne, Ar, Kr, or Xe? To determine which gas is in the sample, we must determine the molecular mass of the gas. This can be done with the ideal gas law: PV = nRT = (m/M)RT where m = the mass of the gas in grams, and M = molar mass of the gas in grams/mol. Solving for M, one gets M = mRT/(PV) = (0.102 g)(0.0821 L atm K 1 mol 1 )(300 K) / (0.242 atm)(0.260 L) M = 39.9 g/mol; the gas is argon . 2. A 0.02864 g sample of vitamin A, a compound consisting only of carbon, hydrogen, and oxygen, is burned to form 0.08802 g of carbon dioxide and 0.02703 g of water. Calculate the percentage of each element in vitamin A. Mass of C in vitamin A = 0.08802 g CO 2 × (12.01 g C)/(44.01 g CO 2 ) = 0.02402 g C Mass of H in vitamin A = 0.02703 g H 2 O × (2.016 g H)/(18.016 g H 2 O) = 0.003025 g H Mass of O in vitamin A = total mass of vitamin A - mass of C - mass of H = 0.02864 - 0.02402 - 0.003025 = 0.00160 g O % C = (0.02402 g C)/(0.02864 g sample) × 100 % = 83.87 % C % H = (0.003024 g H)/(0.02864 g sample) × 100 % = 10.56 % H % O = (0.00160 g O)/(0.02864 g sample) × 100 % = 5.59 % O 3. Acrolein, the eye-irritating ingredient in fumes from burning fat, contains 64.3% carbon, 7.2% hydrogen, and 28.5% oxygen by mass. a) Calculate the empirical formula for acrolein. The formula has general form C x H y O z . The actual ratio of moles is determined by considering an arbitrary amount of the substance, say 100 g (so that mass = % mass). If we assume 100 g of acrolein, then we have 64.3 g C, 7.2 g H and 28.5 g O.

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## This note was uploaded on 02/05/2010 for the course PHYSICS 1D03 taught by Professor N. mckay during the Spring '08 term at McMaster University.

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1e03-tut1-a - CHEM 1E03 TUTORIAL#1 solutions 1 A sample of...

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