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    A tablet of aspirin was weighed and dissolved in 120ml water. The solution (10ml) was placed in a boiling tube and 18ml of 0.25M sulphuric acid was added and put on heat for 25 mins kept on the boil.

    My question is why was the sulphuric acid added?
    I think it is used as a catalyst but I'm not sure what for or how.
    Many thanks in advance
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    Anyone help?
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    (Original post by RedPixie)
    A tablet of aspirin was weighed and dissolved in 120ml water. The solution (10ml) was placed in a boiling tube and 18ml of 0.25M sulphuric acid was added and put on heat for 25 mins kept on the boil.

    My question is why was the sulphuric acid added?
    I think it is used as a catalyst but I'm not sure what for or how.
    Many thanks in advance
    I would say that sulphuric acid is added to make sure aspirin is dissolved in water. Even if sulphuric acid is watered down, it is still strong enough for the tablet.
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    It's difficult to say anything here about why they would do something when we don't know what their end goal is.

    Given that aspirin contains an ester group, the sulfuric acid may be a catalyst for ester hydrolysis (this would explain the boiling). I am not sure why anyone would want to do this though.
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    Yeah that's were I'm confused it goes on

    -Allow the solution to cool and filter any residue
    -Add 2ml of iron (III) complex

    The end is to test the sample in a UV spectrometer
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    It probably is being hydrolysed then. Aspirin would be hydrolysed to ethanoic acid and salicyllic acid, which is poorly soluble in water, so it would then be removed. You would end up with a solution of 1 mol of ethanoic acid for every 1 mol of aspirin that was originally in the tablet (more or less, since ester hydrolysis is reversible). When you add the iron complex, it would likely change this complex somehow, although you would need to know what kind of complex is added to be able to predict the colour change, which is what you are aiming to measure with the spectrometry.
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    Thanks for your help!
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    (Original post by lizardlizard)
    It probably is being hydrolysed then. Aspirin would be hydrolysed to ethanoic acid and salicyllic acid, which is poorly soluble in water, so it would then be removed. You would end up with a solution of 1 mol of ethanoic acid for every 1 mol of aspirin that was originally in the tablet (more or less, since ester hydrolysis is reversible). When you add the iron complex, it would likely change this complex somehow, although you would need to know what kind of complex is added to be able to predict the colour change, which is what you are aiming to measure with the spectrometry.
    Well, well. nice explanation. Have not thought about the complexes in this context.
 
 
 
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