October 17, 2021, 09:13:18 PM
Forum Rules: Read This Before Posting


Topic: Simple distillation Questions  (Read 405 times)

0 Members and 1 Guest are viewing this topic.

Offline yip

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Simple distillation Questions
« on: September 25, 2021, 10:40:17 AM »
Hello everyone! I am kinda new to chemistry so please excuse my lack of knowledge in this field hahaha.. anyways I conducted a simple distillation by adding 10ml of ethanol and a non-volatile red colouring to understand the principles of simple distillation.

1)I measured the temperature every minute and noticed that during the process, at one point, the temperature rapidly increased, do you know the reason for that phenomenon?

2)As the distillation ended, I measured and had an amount of around 8ml of collected ethanol in my test tube. Do you know the reason for this error and decreased yield?

3)I was wondering what I could do to improve the efficiency of this simple distillation. I did use Teflon tapes to prevent gas leaks..

4)I heard that the distillation process ends once the temperature inside the flask decreases, by chance, do you know the reason for this?


Thank you!

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 4927
  • Mole Snacks: +288/-22
Re: Simple distillation Questions
« Reply #1 on: September 25, 2021, 01:34:53 PM »
It is a Forum Rule (see red link above) that you must provide your attempts to answer a question before we can help you.  With respect to point 3, would you explain what you mean by efficiency?  What happened to the red color in this experiment?
« Last Edit: September 25, 2021, 02:23:27 PM by Babcock_Hall »

Offline yip

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: Simple distillation Questions
« Reply #2 on: September 26, 2021, 11:57:46 PM »
Oh I apologize for that. Here are my attempts at the questions.

1) I am assuming at the point when the temperature increased rapidly, the ethanol started to boil and the vapour fills up the distillation head as ethanol evaporates. The vapour gathering is the cause of rapid increase in temperature. The vapours of ethanol condenses on the thermometer bulb and the vapour is in thermal equilibrium with condensate on the thermometer bulb.

2)Hmm I am really not sure about this. I can't find out the reason for the error and decreased yield..

3) I am also not so sure about how I could improve efficiency. I was thinking about doing fractional distillation but my objective is to just see how simple distillation works, hence I added a non-volatile red colouring. The red colouring, being non-volatile was left in the flask after all ethanol evaporated.

4) I assume that this is when all ethanol vapours are condensed and very little vapour of ethanol is reaching the thermometer to remain in equilibrium with condensate. This is the point when ethanol finishes distilling.

By efficiency, I meant I added 10mL of ethanol along with few drops of non-volatile red pigment and I attempted to distill ethanol to separate it from the pigment. However when distillation ended, I ended up with only around 8mL of ethanol in my test-tube.

Offline yip

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: Simple distillation Questions
« Reply #3 on: September 27, 2021, 12:03:12 AM »
Also, I tried to calculate percentage yield of ethanol. May I know if this is the right way?

I ended up with 6.612g of ethanol at the end. The density of ethanol is 0.789 g/mL in the 20 degree celsius lab. I started with 10mL ethanol.

I used d=m/v to first find the volume of final ethanol to get 8.380 mL of ethanol.
Then I calculated percentage yield by 8.380mL/10mL x 100 = 83.8 %

Is this the right way?

Offline yip

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: Simple distillation Questions
« Reply #4 on: September 27, 2021, 12:26:48 AM »
Adding to the efficiency question:

It means like the way to get more pure alcohol from this distillation process.

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 4927
  • Mole Snacks: +288/-22
Re: Simple distillation Questions
« Reply #5 on: September 27, 2021, 07:56:21 AM »
1) Your answer looks reasonable.

2) Some ethanol vapors might have been lost .  This might depend on how well the glassware fits together.  I think you may have hinted at this already.

3) Another meaning of efficiency is how complete the separation of ethanol from another liquid is, but I don't believe that this applies in the present case.  Fractional distillation should outperform simple distillation in this respect.

4) As a general safety rule, one does not distill to dryness.  Of course, this reduces the recovery.

Offline yip

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: Simple distillation Questions
« Reply #6 on: September 29, 2021, 10:49:34 AM »
Thank you so much for your quick responses!

3) Do you have any other ideas I could do to increase the efficiency of this distillation? Other than doing fractional distillation

Sponsored Links