posted by ochem on .
For a Grignard reaction, if you start with 3.97 mL of pure bromobenzene and 0.733 g of 1-phenylethanone, what is the theoretical yield of 1,1-diphenylethanol?
This is a typical limiting reagent problem. I solve these this way.
I assume the equation is 1:1 for all reactant and products but if it isn't you need to write the equation and balance it.
Take the first reagent, convert grams to mols (mols = grams/molar mass), then convert to mols of the product.
Take the other reagent, convert to moles of the reagent then to mols of the product.
You likely will obtain two different values for mols of the product and both can't be right. The correct answer in limiting reagent problems is ALWAYS the smaller value (and the reagent producing that value is the limiting reagent). Then convert the smaller value for mols into grams (g = mols x molar mass). That is the theoretical yield.