That was about what I thought. I assumed I was missing some info.
Hobo Send a noteboard - 09/05/2011 08:50:00 PM
So we were given this question forever ago in my class, and he said we would go over it on a later day in class, but whether he forgot or I wasn't there I never saw the answer to it. And now, school is over for the summer so I can't ask him, but it's been bugging me, so hopefully someone here will know what to do.
A series of measurements are made in order to determine the molar mass of an unknown gas. First, a flask is evacuated and found to weigh 134.567 g. It is then filled with the gas to a pressure of 735 mm Hg at 31 degrees C and found to weigh 1067.9 g. (The density of the water at this temperature is 0.997 g/ml.) Assuming that the ideal-gas equation applies, calculate the molar mass of the unknown gas.
Found the below response, bolded mine, by searching your question with a straight cut and paste, I'd link it but it doens't have a specified address for some reason:
A series of measurements are made in order to determine the molar mass of an unknown gas. First, a large flask is evacuated and found to weigh 134.567 g. It is then filled with the gas to a pressure of 735 torr at 31°C and reweighed; its mass is now 137.456 g. Finally, the flask is filled with water at 31°C and found to weigh 1067.9g. The density of water at this temperature is 0.997 g/mL. Assuming that the ideal-gas equation applies, what is the molar mass of the unknown gas.
PV=nRT moles = grams/molar mass
PV=(g/MM)RT
Molar Mass = gRT/PV
MM=gRT/PV
Mass of gas = 137.456-134.567 = 2.889g
1067.9-134.567=933.3g H2O
933.3g/0.997=936.14mL H2O <--- Volume of container
Volume of container = .9361L
735torr = 0.967atm
MM = (2.889g * 0.0821L*atm/mol*K * 304K)/ (0.967atm * 0.9361)
MM = 79.7g/mol
So just checking, what with the water and all, did you leave that out or did the original question leave it out?
I copied the problem word for word on here. I may have to track my professor down and find out what he wanted. I hate not knowing the answer to questions.
Stand Back!! Im going to attempt science!!
Partaker of the Elixir of True seeing, and Yuna's most trusted advisor.
Partaker of the Elixir of True seeing, and Yuna's most trusted advisor.
Chemisty Question
- 09/05/2011 06:11:03 PM
608 Views
Isn't there some kind of information missing? Like a volume?
- 09/05/2011 07:07:49 PM
431 Views
Yeah, it seemed like the water was kind of randomly thrown in there. I gave all the info I had. *NM*
- 09/05/2011 08:54:30 PM
227 Views
Seems like a measurement on water is left out here
- 09/05/2011 07:18:58 PM
818 Views
Boba Fett smiley is irritating
That was about what I thought. I assumed I was missing some info.
- 09/05/2011 08:50:00 PM
564 Views
Re: That was about what I thought. I assumed I was missing some info.
- 09/05/2011 09:29:36 PM
467 Views