percentage yield paracetamol help plzzzzzzzzzz?

Question

i am really stuck on this.....i got the following equation
C6H7NO + C4H6O3-----C8H9NO2 + C2H4O2
the following info

specific density of acetic anhydride (C4H6O3) is 1.08g/ml
relative molecular mass of paracetamol (C8H9NO2) is 151.2
in an experiment you found out the

mass of 4-aminophenol ( C6H7NO) is 3g
mass of paracetamol is 4g
what is the percentage yield?

10 pts for anyone who can help, many thanks

Jim

Answer 1

A percent yield is just the comparison between the actuall, recovered yield of product divided by the amount that theoretically could have been formed from the quantities of reactants used.

First calculate how much of the paracetamol you should get if 100% yield: (I am having to assume there is sufficient acetic anhydride to completely react all the starting material, since no starting weight or volume for this reactant was given).

Moles reactant (4-aminophenol) =

3g/[(6 x 12.01) + (7 x 1.01) + 14.01 + 16.00] = 0.0275mol

Assuming the equation (and formulas of the substances) are correct, for each molecule of 4-aminophenol, you should get one molecule of paracetamol. (1:1 reactant to product ratio). So, we should get the same number of moles of paracetamol as we had for the reactant (0.0275 mole). So, if the yield was 100%

0.0275mole x [(8 x 12.01) + (9 x 1.01) + 14.01 + (2 x 16.00) =

4.16g of paracetamol should have been produced.

To get % yield, divide the amount actually isolated by the amount that theoretically could have been formed:

4.00g/4.16g x 100% = 96.2% yield.