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Aspirin Synthesis: Yield and Description

I really need help on this today, or at the latest, I need it by 12pm Tuesday 23rd. So I'd really appreciate if anyone could help and + rep to anyone who does, as a little thank you :smile:

I have an experiment on Aspirin synthesis, and I really need help with 2 questions.

1) Calculate the the percentage yield (based on moles) of crude aspirin.

Information I am given:
Molar mass of salicylic acid = 138
Molar mass of asprin = 180

I know how to calculate percentage yield. My question is what percentage should I be expecting, roughly?

2) Describe Aspirin (after crystalisation)

What should I expect it to look like? i.e what is the mark scheme likely to be looking for.

Edit: Also, if anyone can link to a mark scheme for a practical on Aspirin synthesis I would be eternally grateful, thanks.

(edited 11 years ago)

Reply 1

illusionz

Original post by Freyma

I'd expect anything between 60-80% yield to be honest. Depends on how many steps and what purification methods you used.

As for the appearance, again depending on purification method either a white powder or a white crystalline solid.

Reply 2

Freyma

Original post by illusionz

Thanks for the response. I used a Büchner funnel twice to purify it. How will this effect my results?

Reply 3

illusionz

Original post by Freyma

Thanks for the response. I used a Büchner funnel twice to purify it. How will this effect my results?

If you didn't perform a recrystallisation then I'd expect you've got a powder rather than crystals right?

Also assuming you only washed the solid with cold solvent on the funnel your yield should be fairly good.

Reply 4

Freyma

Original post by illusionz

I did do a recrystallisation.

Reply 5

illusionz

Original post by Freyma

I did do a recrystallisation.

Oh, you just said you used a Buchner Funnel which isn't very descriptive!! If you did a recryst then you should have some nice shiny white crystals. However a recryst can do horrible things to your yield so could be anything from 50% upwards really.

Reply 6

Freyma

Original post by illusionz

Oh, you just said you used a Buchner Funnel which isn't very descriptive!!

I'm Sorry. :cry2:

Original post by illusionz

If you did a recryst then you should have some nice shiny white crystals. However a recryst can do horrible things to your yield so could be anything from 50% upwards really.

Okay, thank you for the help.

Reply 7

mytutoring

it could depend on a whole lot of things, just write up your results as you found them. embelishing can result in v serious consiquences. if this is an UG course you can fail for making data up.

Reply 8

Freyma

Original post by mytutoring

it could depend on a whole lot of things, just write up your results as you found them. embelishing can result in v serious consiquences. if this is an UG course you can fail for making data up.

I plan to. However, I wouldn't have used the words "crystaline solid" had I not made this thread. That was my purpose. To get the terminology right

Reply 9

sunshinesmile10

your percentage yield may be over 100% due to excess water...
also the aspirin should be white crystals. Probaly have some unreacted Salicylic acid in there too so if youve dried it properly maybe about 70% yield