Room for Secret and S007

Secret

11:23

Suppose I have 95% ethanol water mixture (i.e. 5% water ethanol mixture). and I started to boil away the azeotrope in the mixture. Does that means 4.4% of the 5% water ethanol mixture is being removed from the boiling flask?

I understood that the azeotrope will boil away as if it is a pure liquid, but what I am not very sure is if I have slightly more water than the azeotrope, how will the concentration of water in the ethanol water mixture changes as I boil away the azeotrope?

^ that is the graph I am talking about earlier

Sir Cumference

Morning

Mew

sup all

Anonymous

@Secret Let us understand using the phase diagram. What happens when you boil a 95 percent mixture ? How does the vapour concentration differ from the mixture's concentration ?

Secret

the amount of ethanol in the mixture will increase and tends towards 95.6% in the vapor phase. For the remaining liquid composition in the boiling flask, I am not sure

So say after boiling the 95% mixture for the first time, I will get a vapor of e.g. 95.4%

Anonymous

Just try to understand that ethanol will vapourize more rapidly compared to water due to its lower BP. So if 95.6 percent ethanol boils off, only a fraction of the whole water present in the initial mixture boils off , right ? Thus, excess water

Anonymous

11:35

Or suppose think of it as moles. We start with 100 moles of mixture. And we have 95 moles of ethanol and 5 moles of water.

Anonymous

On boiling 95 moles of ethanol evaporates along with 4.37 moles of water

Anonymous

Leaving behind 0.63 moles of water in the boiling flask

Anonymous

Get it now ?

Anonymous

@Secret

Secret

Is the boiling off of the mixture linear with time, that is, suppose for each second 1 mole of ethanol is removed, then there will be a corresponding 0.046 moles of water removed, until all 95 moles of ethanol is gone at t=95, leaving behind 0.63 moles water?

Anonymous

11:45

i do not think boiling is a linear function of time. I have never seen any equation like that.

Anonymous

Maybe it is there in higher physics... but I am not sure...

Anonymous

you may make a post on Physics SE main site

Secret

hmm, ok

but at least, I finally understand how the water is left behind, even though I still need to figure out what the shape of that graph will look like. Thanks for helping!

Anonymous

Welcome :)

Anonymous

and I think you can post that as a question about rate of boiling

Anonymous

11:49

anyway, bye for now :)