Simply, theoretical yield is how much of something you produce in theory, while percentage yield is how much of the theoretical yield you actually produce (it measures the efficiency of a reaction).
Sample Theoretial Yield Problem with Steps:
Example: For the balanced equation shown below, if the reaction of 22.8 grams of C3H8O produces 16.7 grams of CO2 what is the percent yield?
2C3H8O + 9O2 --> 6CO2 + 8H2O
Actual Yield = 16.7 grams (actual yield is the product, not the reactant, so since 16.7 grams is produced, it is the actual yield).
We know that CO2 is the limiting reagent because it is the only reactant that is given in the problem.
Find the GFW of the leftest compound in the equation: GFW of C3H8O = 60, so 22.8/60 = .38
You now multiply the ratio of the product to the reactant by .38. (.38 x 6/2 = 1.14)
Multiply the GFW of the reactant (CO2 - 44 g/mol) by the number of moles of the product (1.14). 44 x 1.14 = 50.16 grams.
50.16 grams is the theoretical yield
The percentage yield = (actual yield/theoretical yield) x 100
The percentage yield = (16.7/50.16) x 100
Answer: The percentage yield is 33.3%.
If you understand this problem, you should be set to also solve the percentage yield problems (they are very similiar)!
Now, since you are ready to work more on these problems, go to our worksheet on theoretical yield and percentage yield problems.
