Please help! Last week and this week I did an experiment where we performed ferm
ID: 635242 • Letter: P
Question
Please help!
Last week and this week I did an experiment where we performed fermentation and distillation of ethanol from grape juice. At the end of the experiment during my fractional distillation, we had to get 1 mL fractions (filling 8 test tubes), these 8 test tubes would contain the ethanol. I accidentally mismeasured the 1 mL and instead measured about 0.45 mL in the test tubes. The reason we did 1 mL was to obtain the density of the fractions more easily. When I went to weigh my fractions my first one weighed 0.489 g and it was 0.45 mL. This doesn't make sense to me because the density of ethanol is 0.789 g/mL. My second fraction had a volume of 0.87 mL and the mass was 0.756 g. What did i do wrong? My following fraction masses were 0.453 g, 0.654 g, 0.386 g 0.486 g, 0.494 g.
How do I calculate the density of each fraction? I know density is g/mL but when I do that I get around 1.0 mL which makes no sense because that's not the density of ethanol. Please help!
Explanation / Answer
I thnik it doesn't matter either you take 1 ml or 0.45 ml volume, you will always get correponding weights when you measure the same and hence the density (weight/volume). So if you are getting densities near to 1 g/ml the plausible reasons according to me should be :
1) The fraction you get from fractional distiilation might not be pure ethanol and contains water also or an azeotrope of water-ethanol.
2) There might be some calculation mistakes from your side while measuring the volume and weight.
3) You need to cool the fraction to room temperature before measuring the volume and weight as some of the material may get evaporated at higher temprature in between measuring the volume & weights.
So you need to check the all the possibilties & take corrective measure for the same.