Question is:
If you collected O2(g) and CO2(g) in a 3 liter container with a temperature of 132oF and a total pressure of 1900 torr, and knew that the mole fraction of CO2(g) was .35, how many grams of each gas do you have?

I will donate handsomely with help on what equations I need to do first and how to set up the problem.

pv=nrt

p=pressure, aboslute
v= volume of container
n= moles of ideal gas
r= gas constant
t= temperature , absolute

you have p,v,r, and t
change your temperature to kelvin
solve for n
you know 35% of n is co2
other 65% is o2, molecular weight of O2 is 32 (16 +16) gram/gmol

----
I like to use 0.082057 L atm/(mol k) for gas constant
change 1900 torr to atms , 760 torr in 1 atm

This post was edited by saber_x3 on Jun 25 2015 04:00pm

n=PV/RT so (2.5 atm)(3 liter) / (.0821) (328.705 kelvins) which gave me .277914877

I'm confused, how do I get grams from what I got for n?

This post was edited by chicano on Jun 25 2015 04:10pm

Well, a mole is a specific amount of that element/molecule

if you look at a periodic table like this
http://static.wixstatic.com/media/ed85c2f8c2cb563c55f0e1edf8abc255.wix_mp_1024

You'll see oxygen has a mass of basically 16
you have O2 gas, so 16+16 =32 is the molecular weight (MW)

n*MW=gram of gas
you just solved for n
take your n and multpy by .35 for CO2, .65 for O2

This post was edited by saber_x3 on Jun 25 2015 04:16pm

Not sure if I understood correctly,


so for O2: (.277914877) x (31.9988) = 8.892942566

then I multiply (8.892942566) x .65 = 5.780412668?



This post was edited by chicano on Jun 25 2015 04:30pm

No, look at this statement from the question

" and knew that the mole fraction of CO2(g) was .35"

so, whatever # of moles of gas you have, ONLY 35% is CO2

like saying you have 10 cars, but fraction of red cars is .2 or 2 out of the 10

take your total number of moles, n, multipy it by .35 to get #of moles of CO2
repeat for O2

ok so for CO2: (.277914877) x (.35) = 0.09720206

for O2: (.277914877) x (.65) = 0.18064462

? How do I find grams from here?

The formula is

n*(MW)= # of grams

n is the moles of that substance
MW is the molecular weight of that substance

multiply the n by their respective MW


units of n is moles
units of MW will be grams/mol in your case

This post was edited by saber_x3 on Jun 25 2015 05:04pm

Okay so for CO2: (.092720206) x (44.0098) = 4.27784322 g

and for O2: (.18064462) x (31.9988) = 5.780411066 g

is this correct?

I just want to make sure because the professor is a pretty tough grader.

This post was edited by chicano on Jun 25 2015 05:15pm

Yes
you don't have to carry out your decimals that much, no point
just 2 decimal places will be fine.