In this week\'s experiment you will determine the molar mass of carbon dioxide b
ID: 814805 • Letter: I
Question
In this week's experiment you will determine the molar mass of carbon dioxide by measuring the mass of an Erlenmeyer flask full of the gas. The following calculations are intended to familiarize you with the general procedure:
The mass of an empty Erlenmeyer flask and stopper was determined to be 47.27 grams. When filled with distilled water, the mass was 291.7 grams. The atmospheric pressure was measured to be 0.9289 atm, the room temperature was 24.00oC. At this temperature, the vapor pressure of water is 22.40 torr -- but assume a 50% relative humidity as outlined in the procedure for this experiment.
What is the number of moles of air in the flask?
Moles of air in the flask = mol
If the average molar mass of the gases present in air is 28.960 g mol-1, what is the mass of air in the flask?
Mass of air in the flask = grams
What would be the mass of carbon dioxide in the flask? In this case the CO2 will be saturated with water vapor so assume 100% humidity as outlined in the experiment.
Mass of carbon dioxide = grams
What would be the mass of the flask (and stopper) when filled with carbon dioxide gas?
Mass of flask and stopper filled with CO2 gas = grams
Explanation / Answer
PV= nRT
mass of water in the flask = 291.7g-47.27 g = 244.43 g
volume of water = 244.43 mL (density of water = 1g/ mL) = 0.244L
T = 24oC = 297 K
n = PV/RT = 0.9289 atm *0.244 L/ 0.082 L atm K-1mol-1* 297 K = 9.32 *10-3 mol
moles of air present in the flask = 9.32 *10-3 mol
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mass of air in the flask = moles * molar mass
= 9.32 *10-3 mol * 28.960 g mol-1
= 0.269 g
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mass of Carbon dioxide present in the flask = mole * molar mass of CO2
= 9.32 *10-3 mol * 44 g mol-1
= 0.41008 g
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mass of the flask filled with CO2 = 47.27 g + 0.41008 g = 47.68 g
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