This all-in-one online Percent Yield Calculator performs calculations based on the formula that relates the theoretical yield, actual yield, and percent yield of a chemical reaction. You can enter the values of any two known parameters in the input fields of this calculator and find the missing parameter.
Percent Yield Formula
The percent yield, also referred to as percentage yield, is the percent ratio of actual yield to the theoretical yield of a chemical reaction. In other words, it is calculated as the actual yield divided by the theoretical yield and multiplied by 100%:
Percent yield = (Actual yield / Theoretical yield) * 100%
where
• Actual yield is the amount of a product obtained from a chemical reaction,
• Theoretical yield is the amount of reaction product calculated using the stoichiometry of a balanced chemical reaction equation, taking into account the limiting reactant.
The units of actual and theoretical yield should be the same (moles or grams).
Since the actual yield is usually less than the theoretical value, the percent yield is often below 100%. This is due to incomplete or competing reactions as well as loss of the reaction product during recovery.
However, there are situations when the percent yield can exceed 100%. This means that more of the reaction product was recovered from the reaction than expected. This can happen if there were other reactions that also formed the product. Exceeding can also be the result of an error due to incomplete removal of solvent or other impurities from the sample of the reaction product.
Percent yield indicates the efficacy of a chemical reaction and is considered in various experiments, such as the simple decomposition of a compound, as a measure of the accuracy of the experiment.
Example of Calculating Percent Yield
Consider the reaction of 36.00 g of acetylene (C2H2) and 50.00 g of oxygen, which produces 10.00 g of water. What is the percent yield of water in this reaction?
First write the following balanced chemical equation:
Then, we have to calculate the theoretical yield. For this we need to find the limiting reactant in the balanced chemical equation. The limiting reactant is the one that is in short supply, so that the reaction cannot proceed when it is used up.
To find the limiting reactant, it is necessary to find out how many moles of the initial reactants are involved in the reaction. Then the values found must be compared with the stoichiometric coefficients of the chemical reaction in question.
Molecular weights of C2H2 and O2 are 26.03728 g/mol and 31.9988 g/mol respectively. So, as we can see, the reaction involves 36.00 / 26.03728 = 1.38263 mol of acetylene and 50.00 / 31.9988 = 1.56256 mol of oxygen.
That is, for 1 mole of C2H2 there are 1.56256 / 1.38263 = 1.13 moles of O2. On the other hand, from the reaction equation, we see that for 2 molecules of C2H2 there are 5 molecules of O2. In other words, we have an excessive number of acetylene molecules and, accordingly, the limiting reagent will be oxygen.
Now, we can plug all the data into our Theoretical Yield Calculator: Limiting Reactant (O2) Stoichiometry = 5, Molecular Weight = 31.9988 g/mol, Reactant Mass = 50.00 g; Desired Product (H2O) Stoichiometry = 2, Molecular Weight = 18.01528. And we immediately get Theoretical Yield = 11.25997 g.
And finally, inserting the found value of theoretical yield and actual yield (10.00 g) into our Percent Yield Calculator, we get Percent Yield = 88.81%.
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