Question

Give relation between molar mass and density of gaseous substance

Answer 1

1. The problem statement, all variables and given/known data
The molar mass of carbon dioxide is 0.045kg/mol

Calculate the density of the gas when thetemperature is 273 K and the pressure is 120 000 Pa

2. Relevant equations
Density = mass / volume
pV = nRT
n = mass/ molar mass

3. The attempt at a solution

I frist want to find n to use in pV = nRT to find V AND to find the mass from n = mass/ molar mass, then I want to use this in the Density = mass / volume to find the density

I feel im missing an equation? THe one with that abigardo mumbo jumbo in it?

Thanks :)

Dec 30, 2008

#2

Redbelly98

Try using PV=nRT to find the ratio (n/V), and work from there.

You cannot find n and V with the given information, you can only find their ratio (n/V). But, you can still find the density.

Dec 30, 2008

#3

thomas49th

so would the right way be:

n = mass / molar mass

n = mass / 0.045 

sub this into pv = nRT

V = massRT / 0.045p

sub this into density = mass / volume

density = mass /[(mass x 8.31 x 273)/(0.045 x 120000)]

mass cancels... yay

density = 8.31 x 273 / 45 x 120000

= 0.42 kg/m³

is that right?

Thanks :)

Answer 2

Answer:

$we \: \: have \: \: ideal \: gas \: \: equation \: \: PV=nRT$

$\frac{n}{v} = \frac{p}{RT}$

$replacing \: n \: by \: \: \frac{m}{M}, we get$

$\frac{m}{MV} =\frac{P}{RT}$

$\frac{d}{M} =\frac{P}{RT}$

where d=m/V is the density

$density \: \: d=\frac{MP}{RT}$

$Molar \: \: mass \: \: M=\frac{dRT}{P}$