Limiting Reagents

Yields are usually calculated based on the limiting reagent.

It is rare that two chemicals are mixed together in exactly the right amount. Often there is not quite enough of one chemical; this chemical is the limiting reagent.

 

For example, you want to make two milk shakes using the following recipe.

If you have only 1 scoop of ice cream left, no matter how much milk you have
you can only make 1 milk shake.

A chemist combines 3.00 g Ca and 13.00 g Br2. How much CaBr2 can the chemist make?

If 1.3 mol Na are mixed with 0.60 mol of Br2 how much NaBr will be formed,
and how much of the reagent that is present in excess will remain when the reaction is done?

12.5 g of sodium sulfate and 35.0 g of barium nitrate react to form sodium nitrate and barium sulfate.
9.5 g of barium sulfate were collected. Determine the percent yield of barium sulfate.

Also determine the amount of the unreacted reactants left over at the end of the reaction.