In this week\'s experiment you will determine the molar mass of carbon dioxide b

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 46.84 grams. When filled with distilled water, the mass was 301.2 grams. The atmospheric pressure was measured to be 0.9109 atm, the room temperature was 20.00oC. At this temperature, the vapor pressure of water is 17.50 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

First you need volume: 301.2-46.84=254.36 g

that is 0.25436 L

for the pressure : 17.5/760=0.023 atm

P=0.9109-.5*0.023=.8994

using the formula:pv=nRT

n=0.8994*0.25436/((20+273.15)(.0821))=0.00951. This is the mole of air

Mass of air: 28.97*0.00951=0.2754

So mole of CO2=0.009384

mass of CO2=44*0.009384=0.41289

the volume =46.84-mass of air+mass of CO2

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