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### Topic: [SOLVED] Gases -- Finding volume percentage  (Read 5851 times)

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#### hwgw

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##### [SOLVED] Gases -- Finding volume percentage
« on: January 26, 2008, 08:25:42 PM »
Hi,

I have a question where I am given a sample of a mixture of gases (C2HF5 and C2H3F3) and was told to find the volume percentage of one gas.

Pressure = 0.449 atm
T= 288.15 K
Density= 1.79 g/L

I have also found the average molecular mass to be 94.266 amu.

So how can i approach this question to find the volume percentage of C2H3F3?
Do i use PV=nRT?

Thanks
« Last Edit: January 28, 2008, 01:55:18 AM by 2RIP »

#### Yggdrasil

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##### Re: Gases -- Finding volume percentage
« Reply #1 on: January 27, 2008, 01:11:42 PM »
What's the molecular mass of C2HF5?  What's the molecular mass of C2H3F3?  What ratio of the two gasses gives an average molecular mass of 94.266?

#### hwgw

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##### Re: Gases -- Finding volume percentage
« Reply #2 on: January 27, 2008, 06:22:35 PM »
When asking for average molecular mass, is that (mass 1 + mass 2) / 2 ?

#### Kryolith

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##### Re: Gases -- Finding volume percentage
« Reply #3 on: January 27, 2008, 06:30:03 PM »
No. You need to solve two equations:

x*M(C2HF5)+y*M(C2H3F3)=94.266 g/mol
x+y=1

x=percentage of C2HF5
y=percentage of C2H3F3
M=molar mass
94.266 g/mol = average molar mass of the mixture

#### hwgw

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##### Re: Gases -- Finding volume percentage
« Reply #4 on: January 28, 2008, 01:55:03 AM »