Consider the following date gathered in a \"Molar Mass of a Gas\" experiment. *
ID: 558068 • Letter: C
Question
Consider the following date gathered in a "Molar Mass of a Gas" experiment.
* Mass of the empty reaction test tube: _____27.54_____ g
* Mass of the test tube and MnO2 used in the reaction: ____28.04___ g
* Mass of the test tube, KClO3 (MM = 122.55 g/mol) and MnO2 used in the reaction: ____29.31___ g
* Mass of the test tube and its contents after the reaction: ____28.83_____ g
* Volume of the bubble of oxygen generated in the experiment: ___ (3.60x10^2) ___ mL
* Atmospheric pressure in the lab: ______ (7.4380x10^2) ______ mm Hg
* Vapor pressure at reaction temperature: _____18.6_____ mm Hg
* Temperature: ____21.0____ deg. C
Calculate the experimental molar mass of dry oxygen under those conditions.
Explanation / Answer
mass of Oxygen = (29.31-28.83) = 0.48 g
for moles of O2:
PV = nRT
n = PV/(RT)
Pgas = PTotal - Pvapor = 743.80 - 18.6 = 725.2
n = PV/(RT)
n = 725.2*(0.360)/(62.4*(273+21))
n = 0.014230
MM = mass of O2 / moles of O2 = 0.48 /0.014230 =33.73 g/mol
accepted values is 32 g/mol