Chemistry Forums for Students > Physical Chemistry Forum

Ethanol/Water Distillation Question: Distilland Composition

(1/1)

Cheshyre:
So, when EtOH and Water are distilled, they reach the 78.17C minimum-boiling azeotrope, at which point the compositions of the vapor and liquid are the same. That would mean that the liquid distilland will be 4% water and 96% EtOH by mass.

However, in looking through my old P-Chem notes, I found that the professor noted that the distilland will be composed of pure water. From what I understand, the distilland is supposed to be the sample that is left in the distillation flask, and the distillate is in the receiving flask. I would assume that both flasks contain the same mixtures. Is it possible for the distilland to be pure water?

Also, from a 50% EtOH/50% water mixture, is it possible to go towards making a pure water distillate by heating the vapor to, say, 100C, and then collecting the vapor and condensing it?

Thanks much!

technologist:
I dont know how is it possible to get pure Water in the distillation process for an azeotrope. Even with entrainer U will get a mix of both.

Reg 50% mixture, U can not vaporize the water (BP -100°C) without vaporizing Ethanol (BP - ~78°C). So no question of getting pure water at the top.

Clearly define your objective so that some useful suggestion can be discussed. Do not float your idea upfront....first state the objective & then let all discuss different possibilities.

Hacktacular:
Hi,

Bit late to the party but in case you were still wondering and have spent the past 12 years struggling with sleepless nights... The azeotrope will boil over until there's no longer an azeotropic composition, i.e. the ethanol/water will boil over until there's no more ethanol left in which case you're left with pure water (assuming the water is in excess). On the other side of the coin, if you had a 98% EtOH/water mixture you would bring over your azeotrope (boils at a lower temperature than pure EtOH) until your distilland was pure EtOH.

Enthalpy:
When distilling Schnaps, the recovered booze decreases its alcohol contents progressively.

Navigation

[0] Message Index