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Finding Max Volume for evaporation need help 
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#1
May1014, 09:23 AM

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So this is the problem that I am working on. It is a woosh bottle where I am inputting 70% isopropyl alcohol, closing the top and waiting for the alcohol to evaporate. This mixture is then ignited to generate a flame. My job for this project is to calculate the maximum volume of 70% isopropyl alcohol where all of the alcohol evaporates.
Here hows I attempted to solve the problem Knowns P*(init)=1atm V=2L T=298k Then I just started writing up equations V=Vliq+Vgasinit %I am saying that the inital amount of gas in my 2L bottle plus the volume of the alchol is equal to the total volume in the container. Pinit*Vgasinit=n(init)*R*T %Perfect gas law for the container originally n(init)=n(O2)+n(N2) %The has is just oxygen and nitrogen as first (air) .21n(init)=n(O2) .79n(init)=n(N2) n(final)n(water)n(alcohol)=n(init) %The number of moles after the fuel has evaporated and come to equilibrium with air P(final)*V=n(final)*R*T n(final)=n(alcohol)+n(H2O)+n(O2)+n(N2) %The n alcohol is the 70% of the isopropyl and 30% is water which is where I got the n(H20) I been looking at this problem for hours and can seem to figure out where to go. With the amount of equations I have made up, I have way morre unknowns than equations. Is there something to do with raoults law that I can do or this problem just not possible with the amount of information that I know. Any help would really be appreciated. 


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