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 57.43 grams. When filled with distilled water, the mass was 296.9 grams. The atmospheric pressure was measured to be 0.9242 atm, the room temperature was 21.00oC. At this temperature, the vapor pressure of water is 18.60 torr -- but assume a 50% relative humidity as outlined in the procedure for this experiment. 1.)What 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? Mass of carbon dioxide = ______grams 4.)What would be the mass of the flask (and stopper) when filled with carbon dioxide gas? In this case the CO2 will be saturated with water vapor so assume 100% humidity as outlined in the experiment. Mass of flask and stopper filled with CO2 gas = ______grams

Explanation / Answer

mass = 308-56.97 = 251.03g

for water assume 1g=1ml

so 251.03ml to m^3 we divide by 10^6

so VOLUME= 251.03/10^6 = 2.5103 * 10^-4m^3

Pressure at19^oC = 16.5/ 760 =0.02171 atm

Partial pressure = 0.02171 * .50 = 0.010855atm

Pressure due to air alone= 0.9761-0.010855 = 0.96524 atm

atm to Pa ( Nm^-2) we multiply by normal atm P ( 1.10 * 10^5)

So Pressure due to the air alone = 0.96524* (1.01*10^5) = 9.749025 *10^4 Pa

PRESSURE = 9.749025 *10^4 Pa

TEMPERATURE = 19+273.15 =292.15K

MOLAR GAS CONSTANT(R) = 8.314 J K^-1 mol^-1

u have P, V, R and T

so using PV=nRT

n= PV/RT

(9.749025 *10^4) * (2.5103 * 10^-4)
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