Molar percentage yield

I have this assignment I am working on and we have to calculate the molar percentage yield of a product. I am not to sure what they mean by this.

This is what I have done so far

Weight of paper = 1.02 g
Weight of paper with pure benzocaine = 1.17 g
Weight of pure benzocaine: 1.17-1.02 = 0.15 g

Percentage Yield

Initial weight ×100
Final weight

0.15 g ×100 = 29%
0.52 g

What do they mean?

Reply 1

oceane

No, yield is calculated as a percentage of what theoretically you could have got from the equation. What were your starting materials & what was the equation of the reaction?

If, for example you have an equation with 1:1 mole ratio of reactant and product, and you use 0.5mol of reactant you should theoretically get 0.5mol of product. If you weigh your product (0.15g in your case) and calculate what that is in moles (find the molar mass of benzocaine and how many moles 0.15g represents), then the yield is:

no. of moles recovered/ no.of moles theoretically produced x 100%

Reply 2

Barça

So basically I calculate the number of moles for p-aminobenzoic acid( which is the reactant along with ethanol) and then the number of moles of ethyl p-aminobenzoate benzocaine (product). then I divide the no. of moles of ethyl p-aminobenzoate benzocaine by p-aminobenzoic acid. then multiply the figure you get by 100 to get the percentage.

Is that correct?

Reply 3

IChem

Calculate number of mols of reactant and thus number of mols of product, then you can from that get the mass of product.

This is the theoretical amount of product formed.

You need to find how much product is actually made (this should be given in grams) you then divide this value by the molar mass to get the actual amount of product formed.

by dividing the actual amount by the theoretical amount and multiplying by 100, you should get a value for the molar percentage yield