# Finding density

## 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.

D=M/V

## The Attempt at a Solution

hage567
Homework Helper
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?

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)

hage567
Homework Helper
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).

ok......got that figured out.....thanks for your help. Came out to be .760kg/m^3.

hage567
Homework Helper
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.