The mass of an empty Erlenmeyer flask and stopper was determined to be 51.28 gra
ID: 875356 • Letter: T
Question
The mass of an empty Erlenmeyer flask and stopper was determined to be 51.28 grams. When filled with distilled water, the mass was 306.4 grams. The atmospheric pressure was measured to be0.9254 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.
1What is the number of moles of air in the flask?
Moles of air in the flask = mol
2 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
3 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
4 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
(1) RH = pw/pws x 100
22.4 torr = 0.03 atm = 29.86 mb
Pressure at 50%RH = 0.015 atm
We have, PV = nRT
n = PV/RT
Volume = 306.4 - 51.28/1 = 255.12 mL
Moles of air in flask
n = 0.015 x 255.12/0.9254 x 0.0821 x 297
= 1.73 x 10^-4 mole
(2) Mass of air in flask = 1.73 x10^-4 x 28.96 = 5.0 x 10^-3 g
(3) Mass of CO2 = 5 x 10^-3 x 1.5 = 7.5 x 10^-3 g
(4) Mass of flask with CO2 and air is approximately close to 51.28 g
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