Chem prac help!

[Pandemonium]

Actually, a little modification.

Assuming that the reaction requires 10 minutes to fully react, find the yield after the 10 minutes.

Then take the yield for the latter two another 10 minutes later.

If the results are like this (making up numbers):

10 MINUTES                      3-4 drops                        ample
                                         5g                                 15g
20 MINUTES                      3-4 drops                        ample
                                         17.5g                           17.6g

you can pretty much deduce whatever I said before.

[Mao]

i've read this somewhere, that sulfuric acid in this reaction doesnt really act as a catalyst.

H2SO4 is a strong dehydrating agent, since esterification is an equilibrium reaction [as most things are] with water on the RHS, lowering [H2O] will result in the equilibrium moving to the right.

but i'm not sure about activation energy.


oh, and, how do you propose to calculate the yield? techniques on separating unknown amount of sulfuric acid from the ester?

on that note, if you are going to do it by "smelling", also keep in mind that sulfuric acid has a strong smell on its own. probably not a good idea to say that the "ample" solution has lower yield because it didnt smell as strong, because that could be a result of these two mixing.

as well as, stoichiometric amounts of alkanol and carboxylic acid must also be added, and must be allowed to react fully to produce the smell (and they too! have their own odours)

its very tricky unless you are going to do fractional distillation for your esters =)

[Pandemonium]

^ well i was explaining with the synthesis of aspirin in mind.

weigh filter paper
cool down aspirin, forms a cystal of aspirin (very pure)
filter the solid aspirin using a buchner funnel.
weigh dried sample
m(dried sample + filter paper) - m(filter paper) = m(dried sample)

i think same thing can be done with esters. or that's what i'm lead to believe.
i did the esters prac today and the esters were pretty coagulate to near solid.
but its coagularity would probably lead to error when filtering.

[Rosie]

Can anyone provide me with the states of the synthesis of aspirin.
The equation is: C₇H₆O₃+C₄H₆O₃  ----> C₉H₈O₄+CH₃COOH


A commercial product contains 300mg of aspirin in one tablet. If my mass of the aspirin conducted from the experiment was 3.5g. How much aspirin tablets could I make?

 

[Toothpaste]

3.5g = 3500mg

tablets

[Mao]

Can anyone provide me with the states of the synthesis of aspirin.
The equation is: C₇H₆O₃+C₄H₆O₃  ----> C₉H₈O₄+CH₃COOH

I am pretty sure everything is (aq)

[Rosie]

5g of salicylic acid reacts with 0.2mol of acetic anhydride. How much aspirin can be produced if the percentage yield of aspirin is 35%.

And are you sure that the states of the chemical equation of aspirin are in fact all (aq). I heard some were different. Isn't acetic anhydride a liquid in this equation?

[Pandemonium]

you would be right, acetic anhydride would not be called acetic anhydride if it were a solution because it'd react and form acetic acid.

[Rosie]

If salicylic acid is the limiting reactant, calculate the maximum mass of aspirin that could be theoretically obtained using 2.79g of salicylic acid.

For the answered question above, you did not use the 5g of salicylic acid. Don't you first have to work out the mol of salicylic acid and see which is in excess with 0.2mol of acetic anhydride?