# Finding Max Volume for evaporation need help

1. May 10, 2014

### Reegus

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.

2. May 27, 2014