Question

n 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 58.85 grams. When filled with distilled water, the mass was 303.4 grams. The atmospheric pressure was measured to be0.9385 atm, the room temperature was 20.00^oC. 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

Answer 1

Moles of water in the flask = (303.4-58.5) = 224.9 gms

Assuming the density of water to be 1. Volume of water (V)=224.9/1 =-224.9cc =0.2249 liters

Relative humidty =paratial pressure of water vapor/ vapor presure of liquid

Partial pressure of water vapor = 0.5* Vapor pressure of liquid =0.5*17.5 =8.75 Torr = 8.75/760= 0.01153 atm

Partail pressure of dry air (P) = 0.9385-0.01153 =0.92697 atm

T=20+273 =293k

From PV=nRT

R=0.0823 litatm/gmole.K

n=PV/RT = 0.92697*0.2249/(0.0823*293) = 0.008645 gmoles

Mass of air =0.008645*29=0.25gms

Mas of Carbon dioxide =0.008645&44=0.3840gms of CO2

Mas of flask and stopper =58.85+0.3840=59.2304gms