Need Chemistry Help

[BoldAsLove]

I have a chemistry question on my homework that says
The density of a gas at 273K and 760mmHg(1atm) is 4.00g/l. What is its molar mass in g/mol?

Ive got it so far from Pmm=DRT to mm=(4.00g/L)(.0821Latm/molK)(273K)/1atm

The problem is i need to convert the 4.00 g/L to g/mol and im confused about doing this...ive gotten the 4.00L to 4000 mL and apparently i can convert mL to grams but im confused about this part. What do I do, or am I just doing this completely wrong? Please help!

 

[Tiamat]

PV=nRT

D=m/V
V=m/D

P(m/D)=nRT
m/D = nRT/P
m=DnRT/P
m/n = DRT/P

mw = m/n

 

[BoldAsLove]

so this problem cannot be done?

 

[bluewall21]

No, you are at STP, so it is 1 mol/22.4 L to convert to moles.

Either that, or I'm really tired.

 

[BoldAsLove]

so i just time 4 by 22.4?

 

[Hyperion042]

PV = nRT
n = m / M

PV = mRT / M
P 1/(d) = RT / M
M = RTd / P
R = Gas Constant
T = 273 K
d = 4.00 g/L
P = 1 atm.

Plug, chug, solve.

 

[bluewall21]

Originally posted by: BoldAsLove
so i just time 4 by 22.4?

Yeah, I think so.

 

[FleshLight]

PV=(grams of gas/molar mass)RT