In this tutorial, you will learn what percent yield is and how to calculate it. In addition, you will walk through an example calculation.
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What is Percent Yield?
When performing an experiment, there is a maximum yield you can obtain if there are perfect reaction conditions; this is the theoretical yield. However, even if you follow an experiment correctly, it is likely that you will not have a perfect yield of the product; the amount of product you end up with is your actual yield.
The percentage of the theoretical yield you obtained in your experiment is the percent yield. Let’s learn how to calculate it below!
How to Calculate Percent Yield
You can use the equation below to calculate your percent yield from an experiment:
Theoretical Yield Calculation
First, you should calculate the theoretical yield of your experiment; usually, this will involve stoichiometric calculations. By first looking at the chemical equation and information given, you can get an idea of what is reacting and how the product is forming.
Since no more product can be formed once the limiting reagent runs out, the next step is to identify the limiting reagent.
You can then use dimensional analysis to see how much product can be formed based on the amount of limiting reagent that is given. This is the theoretical yield of your experiment.
Actual Yield Calculation
If you are physically doing an experiment, your actual yield will be the amount of product you weigh out on your balance. If you are doing a word problem, the actual yield may be given within the problem.
Percent Yield Equation
The last step, once you have both theoretical and actual yield, is plugging the numbers into the equation. Dividing the actual by the theoretical gives you the fraction of product you made. Multiplying that by 100 gives you the percent yield.
Percent Yield Calculation Example
Now that we know the steps to calculate percent yield, let’s walk through an example:
Use the balanced chemical reaction below. If 40.00 g of Acetylene (C2H2) and 65.00 g of Oxygen are used, and 25.00 g of water are produced, what is the percent yield?
First step is to find limiting reagent & theoretical yield of water:
Using dimensional analysis on both reagents, acetylene is found to produce a lower amount of product than oxygen; because of this acetylene is our limiting reagent.
27.67g is our theoretical yield. The last step is to plug our numbers into the percent yield equation.
Our percent yield is 90.35%.
For more example questions to try, click here!