Percent Yield

  One way to think of percent yield is as a measure of success. To find this number you will need two things: the theoretical yield and the experimental yield. The theoretical yield is the amount of products that should be formed and the experimental yield refers to the amount you're given based on the experiment. Because you are usually given the experimental yield, you will need to find the theoretical yield first...

EX.1:

If you burn 12 g of carbon (C) to produce 48.0 g of carbon dioxide (CO2) what is the percent yield?

1. The first and one of the most important steps is to make sure you have a correct and balanced equation.

C + O₂ --- > CO₂

2. You will then have to find the theoretical yield of carbon dioxide because you are given the experimental value. Take what you have and convert it into moles as it is the most common conversion factor.

12 g of C    x    1 mol of C

                      12.0 g of C

3. Next, use your mole to mole ratio: what you need over what you have. Cancel out what you can.

12 g of C    x    1 mol of C    x    1 mol of CO2

                      12.0 g of C            1 mol of C

4. After having your moles of Carbon Dioxide, use molar mass as your conversion factor and cancel out what you can.

12 g of C    x    1 mol of C    x    1 mol of CO2    x    44.0 g of CO2

                      12.0 g of C            1 mol of C            1 mol of CO2

5. Multiply and divide your equation and you will now have your theoretical yield. Plug it into the percent yield formula.

% YIELD    =    Experimental     x 100

                           Theoretical

% YIELD    =    48.0 g    x    100

                          44.0 g

% YIELD    =    109%

For more examples check out this link:

 http://www.youtube.com/watch?v=TKNxdL7DN1I