Posted by Fiona on .
If 2 g of salicylic acid is heated with 4 g of acetic anhydride, what is the theoretical yield ?
C7H6O3 + C4H6O3 --> C9H8O4 + C2H4O3
This is a limiting reagent problem. You know that because BOTH reactants are listed instead of just one.
1. Convert 2 g SA to moles. moles = gram/molar mass.
2. Convert 4 g acetic acid to moles. Same way.
3a. Convert moles SA to moles product.
3b. Convert moles acetic acid to product.
3c. It is more than likely than the answer from 3a and 3b will not be the same which means one of them is wrong. The correct answer, in limiting reagent problems, is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.
4. Now convert the value from 3c to grams. g = moles x molar mass.