Ethanol Saturation *Urgent* Help please

[TSP31]

I am trying to calibrate a MQ-3 sensor with an arduino uno board, however I have to do a hand calculation to arrive at my theoretical ethanol content (amount of ethanol saturated in the air) before I can calibrate my sensor. The following data is what I have:

3- compound mixture-H20(11.27% or 50 ml) C2H5OH-(Ethanol)(11.27% or 50 ml) and Dry air (77.45% or 343.603ml)

The recording is taking place at room temperature. (23 C)

I am wanting to find the mass of ethanol saturated in the air.

I have tried using implementing the Ideal gas law to find the mass of the air then using the formula for humidity ratio (w=mass_vapor/mass_air) where w= (0.622*Pvapor)/(P-Pvapor)

Applying those three formulas I do get a result for the mass of ethanol in the air.

However I am not taking into consideration the volume of each compound in my mixture.

Is this answer I calculated correct? Or do I have to implement some other thermodynamic relationship involving the volumes or %compunds in my mixture??

 

[MintJulep]

I'm thinking you need to apply some dead English or French men to the situation.

Dalton or Raoult perhaps.

 

[TSP31]

If I apply Dalton's model to this situation how will can I calculate for mass of ethanol in the air, will it not be calculating the mass of all the ethanol in the mixture?

 

[MintJulep]

You're at saturation, so you can look up the quality (ratio of gas to liquid)

 

[MintJulep]

http://webbook.nist.gov/chemistry/fluid/

 

[TSP31]

Ok, that makes sense, but when you say look up quality do you mean from saturation tables for ethanol? Because that would be worth its weight in gold to me, I cannot find them anywhere!

 

[TSP31]

Thanks for the reference, but I may be missing something because i do not see ethanol in the pull down selection. (C2H5OH)

 

[MintJulep]

Did you follow my link?

 

[TSP31]

Yes, and in the pull down selection I can not find ethanol is it there?

 

[MintJulep]

Humm. Didn't imagine that ethanol wouldn't be in there.

 

[TSP31]

I know it is crazy I can not find saturation tables ANYWHERE for ethanol.

 

[IRstuff]

How about:

http://www.ddbst.com/en/online/Online_Calc_vap_Form.php

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[ione]

Another calculator

http://nequam.se/misc/ethanol.php

And a read at the link below:

http://symp15.nist.gov/pdf/p128.pdf

 

[Latexman]

Is the mixture you gave a vapor compostion? H20 (11.27% or 50 ml), C2H5OH (11.27% or 50 ml), and dry air (77.45% or 343.603ml) The reason I ask is it looks a little redundant with % and volume given. Is the volume the partial volume of the vapor space attributed to that component?

If this is all so, calculate an average molecular weight, calculate total number of moles = n = PV/RT, calculate the moles of C2H5OH = 0.1127n, calculate the mass of C2H5OH = moles of C2H5OH x MW of C2H5OH.

Good luck,
Latexman