# Melting point of pure product help needed

Announcements
#1
Give a suitable temperature range over which to collect the final product during the distillation.

I don't get why the answer is between 49 and 53oC, provided it includes 51oC or 50-52. I know that the pure might contain a little bit of impurities so it will having a sightly lower boiling point. However how can it only be as low as 49? I estimated it could be 45-50 C. Also why can the boiling point of the product be slightly higher than the boiling point of the pure product?

Thanks
0
5 years ago
#2
You are not trying to determine the purity of the sample as you do with measuring the melting point of a solid. You are trying to purify a mixture.

Two degrees either side of the boiling point to collect a fraction of good quality should be ample - then comes the analysis to determine the purity.
0
#3
(Original post by EierVonSatan)
You are not trying to determine the purity of the sample as you do with measuring the melting point of a solid. You are trying to purify a mixture.

Two degrees either side of the boiling point to collect a fraction of good quality should be ample - then comes the analysis to determine the purity.
But the solid would have been purified as it has been recrystallized but may contain impurities, I think ? So why does it have to be from 49 - 51 specifically?
0
5 years ago
#4
(Original post by coconut64)
But the solid would have been purified as it has been recrystallized but may contain impurities, I think ? So why does it have to be from 49 - 51 specifically?

Give a suitable temperature range over which to collect the final product during the distillation.
Two degrees either side of the boiling point of the product (51) is a sensible range to collect a good quality sample. If you were then to check the melting point (not mentioned in the question) then you would expect the melting point range to be slightly lower than literature values due to impurities (and not above it as you correctly stated in your OP). Following recrystallisation it should then be closer to the literature value range - but purification is a balance between yield and purity!
0
X

new posts
Back
to top
Latest

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### Poll

Join the discussion

Talking to current university students (17)
18.48%
Talking to peers going through the same thing (31)
33.7%
Speaking to student ambassadors from the universities (5)
5.43%
Speaking to staff members from universities (2)
2.17%
Using the personal statement builder, library or helper service (9)
9.78%
19.57%
Learning about/speaking to Student Finance England (4)
4.35%
Something else (tell us in the thread) (6)
6.52%