Mass of CO2 in flask: Temperature of CO2 gas: pressure of CO2: number of moles o

ID: 546276 • Letter: M

Question

Mass of CO2 in flask:

Temperature of CO2 gas:

pressure of CO2:

number of moles of CO2 in flask (from PV=nRT)

Experimental molar mass of CO2:

average molar mass of CO2:

theoretical molar mass of CO2
(calculate from atomic masses)

% difference in experimental molar mass:

CHMI5ILL.: MOLAR MASS OF A GAS 5 Name Date Score Data and Results (Show detailed calculations on the back of this sheet.) It run 2nd run Mass of stoppered flask + air + tape Air temperature 22 °C oc Mass of stoppored flask and Co, (gas) + tape 31551460 oc 9. Temperature of CO2 (gas) Barometric pressure Volume of water in flask gas) Density of air (from CRC Handbook) Mass of air in flask 73.2 torr | 3.2 2t0 O.310L 0.310 2 Calculating ngas Mass of EMPTY stoppered flask + tape 5 2 7 677 152.7477 Mass of C02 in flask Temperature of CO gas Pressure of CO2 Number of moles of CO2 in flask (from PV nRT) torr torr mol Calculating molar mass g/mol Experimental molar mass of CO2 Average molar mass of CO, Theoretical molar mass of CO2 (calculate from atomic masses) % difference n experimental molar mass mo g/mol

Explanation / Answer

Trial 1

Trial 2

Mass of empty stoppered flask + tape (g)

152.7677

Mass of CO2 in flask = (mass of stoppered flask and CO2 + tape) – (mass of empty flask + tape) (g)

(153.3125 – 152.7677) = 0.5448

(153.1960 – 152.7677) = 0.4283

Temperature of CO2 gas = (temperature in Celcius scale + 273) K

(21 + 273) = 294

(19.1 + 273) = 292.1

Pressure of CO2 gas = (barometric pressure) – (vapor pressure of water at 22°C) (torr)

We take the air temperature to be equal to the temperature of water.

(732 – 19.8) = 712.2

Number of moles of CO2 in flask (mole)

0.01049 (check calculation below as an example)

0.01056

Sample calculation for number of moles of CO2 gas: Convert pressure to atmosphere as P = 712.2 torr = (712.2 torr)*(1 atm/760 torr) = 0.9371 atm; the volume of CO2 is V = 270 mL = (270 mL)*(1 L/1000 mL) = 0.270 L.

Use trial 1 as an example.

n = P*V/RT = (0.9371 atm)*(0.270 L)/(0.082 L-atm/mol.K).(294 K) = 0.01049 mole.

Calculating Molar Mass

Experimental molar mass of CO2 = (mass of CO2 in flask)/(number of moles of CO2 gas) (g/mol)

(0.5448)/(0.01049) = 51.935

(0.4283)/(0.01056) = 40.559

Average Molar mass of CO2 (g/mol)

½*(51.935 + 40.559) = 46.247

Theoretical molar mass of CO2 (g/mol)

(1*12.01 + 2*15.9994) = 44.0088

% difference in experimental molar mass

(46.247 – 44.0088)/(44.0088)*100 = 5.0858% 5.086