[Rotavapor]

Hi there im new here, so please correct me if i do anything wrong 

I have received the following problem:
Determine the boiling point for a liquid alcohol (I have a strong suspicion that i might be ethanol) with this measured data

T (K)	Vapor Pressure(mbar)
277	18.0
283	26.9
303	91.2
318	206
333	432

i may assume that Δ_vapH is independent of temperature.

I have tried to fit the data to (1/T;ln(p/p0), where p0 is the atmospheric pressure, and found a quadratic regression:
y=-46280x²+609.12x-14.141
this should match g(t)=c₀+c₁/T+c₂/T²
at boiling point g(t) should be equal to 0
and therefor T_B=c₁/-c₀
I tried this T_B=609.12/14.141=43.0747K

I knew this was wrong, so i tried to fit a plot to (T;p) and found a exponential regression y=3*10^-6*e^0.057x
and becouse p=p0 at boiling point i solved the equation as
1013.25=3*10^-6*e^0.057x
x=344.25K is this right? also im interested to know if it possible to use the other method? as i later want to use the slope of g(t) to find Δ_vapH = slope*R and then Δ_vapS=Δ_vapH/T_B

[Corribus]

Normally I would use the August equation but the data doesn't seem to give a good linear fit (log[p] vs 1/T).  So you can try fitting to the Antoine equation if you have a good fitting program like Origin.  I'm out of time at the moment but I'll try a little later and see if I come up with anything that makes sense.

[Corribus]

Sorry it took some time to get back to you.  I was in error before because in my haste I typed the data into Origin incorrectly.  You can use the Antoine or August equation.  Probably the problem writer wants you to use the latter because they mention to assume temperature independence of the vaporization enthalpy.  To fit to the Antoine equation you'll need a good fitting program, but you can fit to the August equation with a linear regression in excel.

http://en.wikipedia.org/wiki/August_equation

If you need additional help, let me know.

[Rotavapor]

Thanks I think i got it now, that helped alot