The key difference between theoretical yield and actual yield is that theoretical yield is the value calculated from the equation of the chemical reaction considering stoichiometry, whereas actual yield is what we obtain from the experiment.
It is very important to understand how much product is generated from given quantities of reactants before initiating a particular chemical reaction. This is called the theoretical yield. Using this calculated yield, we can determine how much of each reagent is required to make a certain amount of the product.
CONTENTS
1. Overview and Key Difference
2. What is Theoretical Yield
3. What is Actual Yield
4. Theoretical Yield vs Actual Yield in Tabular Form
5. Summary – Theoretical Yield vs Actual Yield
What is Theoretical Yield?
Theoretical yield is the value calculated from the equation of the chemical reaction considering stoichiometry. In other words, it is the amount of a product collected from the complete conversion of the limiting reactant in a chemical process. However, the amount of product formed from a flawless chemical reaction is not always equal to the actual yield we get from performing the same chemical reaction. Often, the theoretical yield is measured in grams or moles.
Using an example, we can understand the method of calculating the theoretical yield. When making water, hydrogen gas (10 grams) can be burnt in the presence of an excess amount of oxygen gas. Then the total amount of water produced from this process (theoretic yield of water) can be determined as follows:
2H2(g) + O2(g) → 2H2O(l)
Then, the mole ratio can be determined using the 2 moles of hydrogen gas and 1 mole of oxygen gas to make 2 moles of water given in the equation. Therefore, the mole ratio between hydrogen gas and water is 1: 1. Thereafter, we can use the amount of hydrogen gas used (10 grams gives 10 / 2 g/mol = 5 mol) to determine the amount of water created (since it is 1: 1 ratio, this reaction produces 5 moles of water which is equal to 5 mol x 18 g/mol = 90 grams). Then the theoretical yield becomes 90 grams of water.
Moreover, we can use a limiting reactant of a balanced chemical equation to determine the theoretical yield. The limiting reagent is not found abundantly. Therefore, the reaction cannot continue after using up all the limiting reagent moles.
What is Actual Yield?
The actual yield is the amount of the product produced by a reaction. This amount can be higher than a theoretical yield. This is because a subsequent reaction tends to provide more product or because there are impurities in the recovered product. The limiting reagent is not taken into account when determining the actual yield of a chemical reaction.
Usually, when the theoretical yield is 100%, the actual yield is almost always a lower value than 100%. But sometimes, the actual yield goes over 100% when there is an impurity in the product or if there are any unwanted substances present in the yield.
What is the Difference Between Theoretical Yield and Actual Yield?
Theoretical yield and actual yield are important in determining the chemical nature of a chemical reaction. The key difference between theoretical yield and actual yield is that actual yield is the amount of a product we obtain from the experiment, whereas theoretical yield is the value calculated from the equation of the chemical reaction while considering stoichiometry.
The following table summarizes the difference between theoretical yield and actual yield.
Summary – Theoretical Yield vs Actual Yield
The key difference between theoretical yield and actual yield is that actual yield is the amount of a product we obtain from the experiment, whereas theoretical yield is the value calculated from the equation of the chemical reaction while considering stoichiometry. The actual yield can sometimes be higher than the theoretical yield.
Reference:
1. “Theoretical and Actual Yields.” Chemistry LibreTexts, Libretexts, 15 Aug. 2020.
2. “Finding Theoretical Yield – Overview of Theoretical Yield and Finding Theoretical Yield and Faqs.” BYJUS, BYJU’S, 18 Mar. 2022.
Image Courtesy:
1. “Chemical reaction far eastern federal university” By Lena Jaginyan – Own work (CC BY 4.0) via Commons Wikimedia