How do you find the theoretical yield of the product?

Question

54.70 mL of 0.162 M AgNO3
48.30 mL of 0.161 M K2CrO4
Mixing the following solutions resulted in the isolation of 1.37 g of Ag2CrO4

Answer 1

The theoretical yield is the maximum amout that could be created from the reacants provided.

First determine the balanced equation: Ag is +1; NO3 is -1; K is +1; and CrO4 is -2 so:

2 AgNO3 + K2CrO4 ---> Ag2CrO4 + 2 KNO3

Now, determine the number of moles of each reactant:

0.0547 l x 0.162mol/l = 0.00886 mole AgNO3
0.0483 l x 0.161mol/l = 0.00778 mole K2CrO4

You can see that the Ag+ will run out first, because we need 2 of them for each CrO4-2. The quantity of Ag2CrO4 that can be theoretically produced is 0.00886/2 or 0.00443 mole.

To get grams, multiply moles by grams per mole for the compound in question:

0.00443mol x [(107.9 x 2) + 52 +(16 x 4)] =

0.00443mol x 331.8g/mol = 1.46g AgCrO4 (this is the theoretical maximum amount if 100% yield and no losses in isolation etc).

You got 1.37g which is 1.37/1.46 or 93.8%yield.

Answer 2

The theoretical yield is found from the balanced equation of the reaction and your "starting" reagents. (Watch out for the limiting reagent.) If you have one.