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# how many moles of NaOH does aspirin react with? watch

1. some places say 1, others say 2.. others say 3.

I want a decent answer and sound like you know what you're on about... gimme a source, perhaps?

thanks

I may even give a replier a new gem
2. Why do you want aspirin to react with NaOH?

NaOH is required in the synthesis of aspirin.
3. actually i need to know how many moles of salicylic acid react with NaOH too, if anyone can help?

I need to know to do the calculations of a titration between the two

It's seriously annoying that so many different sources say different amounts of moles react, but my results look like it's 1 mole to 1 mole.
4. (Original post by Saffie)
actually i need to know how many moles of salicylic acid react with NaOH too, if anyone can help?

I need to know to do the calculations of a titration between the two

It's seriously annoying that so many different sources say different amounts of moles react, but my results look like it's 1 mole to 1 mole.
Ignore that on 2nd thoughts!

I think one mole would react straight away with the acid group, then one mole would hydrolyse the ester and one mole would then react with the acid produced from the hydrolysis ... so overall 3 moles react.

Are you doing a back titration investigation? because if so, when you use the acid then all the excess NaOH will react but ALSO the phenoxide ion will gain a proton so effectively it will look as if only 2 moles of NaOH reacted.

Does that make sense?
5. Here are three equations I've found for it, the websites never seem to explain it, sorry.

CH3COO.C6H4.COOH + 3NaOH -> CH3COONa + NaO.C6H4.COONa + 2H2O

CH3COOC6H4COOH + 2NaOH -> CH3COONa + HOC6H4COONa + H2O

CH3COO.C6H4.COOH + NaOH -> CH3COO.C6H4.COONa + H2O
6. (Original post by oxymoron)
Ignore that on 2nd thoughts!

I think one mole would react straight away with the acid group, then one mole would hydrolyse the ester and one mole would then react with the acid produced from the hydrolysis ... so overall 3 moles react.

Are you doing a back titration investigation? because if so, when you use the acid then all the excess NaOH will react but ALSO the phenoxide ion will gain a proton so effectively it will look as if only 2 moles of NaOH reacted.

Does that make sense?
I'm doing both an acid/base titration and a back titration, so which equation for each experiment?

Thanks a lot, makes sense

edit: I gave you a shiny gem
7. (Original post by Saffie)
I'm doing both an acid/base titration and a back titration, so which equation for each experiment?

Thanks a lot, makes sense

edit: I gave you a shiny gem
Heh, thanks!

Back titration is definitely the 2nd equation overall assuming you use phenolphthalein as the indicator (ie high pH) as explained above.

For a simple acid/base titration I think it would just be 1 mole because the alkali hydrolysis wouldn't happen without heating and reflux and the NaOH added would just react quickly with the COOH group and then build up an excess after one mol/mol is added.

I think that's right!
8. bleh, what's the equation for salicylic acid and NaOH? Can't find it anywhere.
9. (Original post by Saffie)
bleh, what's the equation for salicylic acid and NaOH? Can't find it anywhere.
C6H4(OH)COOH + NaOH --> C6H4(OH)COO-Na+ + H2O
10. (Original post by Gnarl)
C6H4(OH)COOH + NaOH --> C6H4(OH)COO-Na+ + H2O
cheers, you got a gem too
11. what's the equation for an equimolar mixture of salicylic acid and aspirin against NaOH?

Dya just kinda merge the equations? Such would be:

C6H4(OH)COOH + CH3COO.C6H4.COOH + 2NaOH --> C6H4(OH)COO-Na+ + CH3COO.C6H4.COONa + 2H2O
12. (Original post by Saffie)
what's the equation for an equimolar mixture of salicylic acid and aspirin against NaOH?

Dya just kinda merge the equations? Such would be:

C6H4(OH)COOH + CH3COO.C6H4.COOH + 2NaOH --> C6H4(OH)COO-Na+ + CH3COO.C6H4.COONa + 2H2O
is this right? I really need to know
13. (Original post by Saffie)
is this right? I really need to know
If just a simple acid/base titration then I would say yes. If heating under reflux then doing a back titration then you need to factor in the ester hydrolysis as above.
14. (Original post by oxymoron)
If just a simple acid/base titration then I would say yes. If heating under reflux then doing a back titration then you need to factor in the ester hydrolysis as above.
yup i'm analysing the acid/base titration now, I look forward to the back titration yet to come.

and thanks very much
15. (Original post by Saffie)
yup i'm analysing the acid/base titration now, I look forward to the back titration yet to come.

and thanks very much
thank you for the gem, good luck with the titration!
16. lame questions but im doing back titration for my aspirin analysis but i seem to can't find a good method help plox

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