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Finding density

  • #1
203
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Homework Statement



OK, the problem says to find the molecular weight of NH3.

It is 17.03g/mol.

Next, you are supposed to find the density(in Kg/m^3) for the NH3.

I'm not sure how you do this part. I don't know if I have to convert or what.

I know the actual density is 0.771 kg/m^3.

Homework Equations



D=M/V

The Attempt at a Solution

 

Answers and Replies

  • #2
hage567
Homework Helper
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It's a gas, you can probably treat it with the properties of an ideal gas. Like so many mols of an ideal gas at STP has a certain volume....etc. Think ideal gas law.

Does that help?
 
  • #3
203
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Well kinda I guess.

I know my chemistry(a little)....but I'm just confused(or thinking too much).

I know that at STP....volume is 22.4 L

Temp is 273.15K
Pressure is 1 atm
n is usually 1 mole

So how does that relate to density though....do i just divide my mass by the 22.4?(I can't see the units working out)
 
  • #4
hage567
Homework Helper
1,509
2
Small correction: at STP, the volume of an ideal gas is 22.4 L/mol. Liters are a way of expressing volume, right? So convert that to m^3. You already figured out the molecular mass per mol. Just look at the units (make sure everything is consistent).
 
  • #5
203
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ok......got that figured out.....thanks for your help. Came out to be .760kg/m^3.
 
  • #6
hage567
Homework Helper
1,509
2
Yeah, the 22.4 L/mol isn't exactly the same for all gases, so depending on where you got the accepted value it might vary a bit.
 

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