What is the Difference Between Theoretical Yield and Percent Yield

The main difference between theoretical yield and percent yield is that theoretical yield is the maximum amount of product that can be obtained from a chemical reaction, assuming that the reaction proceeds to completion and all reactants are converted into products without any loss, whereas percent yield is a measure of the efficiency of a chemical reaction in the laboratory.

Theoretical yield and percent yield are concepts fundamental to chemical reactions, offering insights into the efficiency of a reaction in a laboratory or industrial setting.

Key Areas Covered

1. What is a Theoretical Yield
      – Definition, Example, Applications
2. What is a Percent Yield
      – Definition, Features 
3. Similarities Between Theoretical Yield and Percent Yield
      – Outline of Common Features
4. Difference Between Theoretical Yield and Percent Yield
      – Comparison of Key Differences
5. FAQ: Theoretical Yield and Percent Yield
      – Frequently Asked Questions

Key Terms

Theoretical Yield, Percent Yield

What is a Theoretical Yield

The theoretical yield is a fundamental concept in chemistry, often denoted as Y theoretical, and it is used to predict the ideal or expected outcome of a chemical reaction. It provides chemists with a valuable benchmark, helping them understand the maximum amount of product that can be obtained under specific conditions.

At its core, theoretical yield is a calculated value, and it is derived from the stoichiometry of the chemical reaction. Stoichiometry is the study of the quantitative relationships between the reactants and products in a chemical reaction, as determined by a balanced chemical equation.

Let’s illustrate the calculation of theoretical yield with a simple example:

Example

The synthesis of water (H₂O) from the reaction of hydrogen gas (H₂) and oxygen gas (O₂):

Balanced Chemical Equation: 2H₂ + O₂ → 2H₂O

In this reaction, we have a 2:1:2 stoichiometric ratio between hydrogen, oxygen, and water molecules.

Start with the moles of the limiting reactant. Suppose we have 5 moles of hydrogen (H2) and 2 moles of oxygen (O2).

Identify the limiting reactant. To do this, calculate the moles of water that can be formed from each reactant. The theoretical moles of water from 5 moles of H₂ are (5 moles H₂) x (2 moles H₂O / 2 moles _H2) = 5 moles H₂O. The theoretical moles of water from 2 moles of O₂ are (2 moles O₂) x (2 moles H₂O / 1 mole O₂) = 4 moles H2O. Since the theoretical moles of water from O₂ are lower, O₂ is the limiting reactant.

Now, calculate the theoretical moles of water formed from the limiting reactant. In this case, it is 4 moles of H₂O.

To obtain the theoretical yield in grams, you can use the molar mass of water, which is approximately 18 grams/mole (2 g/mol for hydrogen and 16 g/mol for oxygen). Therefore, the theoretical yield in grams is (4 moles H₂O) x (18 g/mole) = 72 grams of water.

So, in this example, the theoretical yield of water is 72 grams when 5 moles of hydrogen and 2 moles of oxygen react under ideal conditions. However, achieving this yield in practice may be challenging due to real-world factors like incomplete reactions or impurities.

Figure 1: Relation Between Conversion Selectivity and Yield

Applications of Theoretical Yield

The concept of theoretical yield has practical applications in various industries and everyday contexts. In pharmaceutical manufacturing, precise theoretical yield calculations are vital for efficient production processes and quality control. Agriculture benefits from theoretical yield calculations by optimizing the application of fertilizers and pesticides, guaranteeing crops receive the appropriate nutrients and protection. The food industry relies on these calculations for recipe scaling, production efficiency, and product consistency.

Chemical engineers use theoretical yield calculations in designing and optimizing industrial processes, spanning petrochemical production to wastewater treatment. Additionally, in environmental sciences, these calculations predict product formation in environmental reactions, contributing to the understanding and mitigation of pollutants.

What is a Percent Yield

Percent yield, often denoted as % yield, is a measure that quantifies the efficiency of a chemical reaction by expressing the ratio of the actual yield to the theoretical yield as a percentage. It provides an indication of how much of the expected product was obtained in a real-world scenario. The formula for calculating percent yield is as follows:

The actual yield represents the quantity of product obtained in the laboratory or industry, while the theoretical yield is the maximum amount of product that could be produced under ideal conditions. By comparing these two values, chemists and engineers can assess the extent to which a reaction was successful and whether there were any inefficiencies or losses during the process.

Furthermore, the concept of percent yield has far-reaching applications across diverse fields, influencing aspects of daily life that may not be immediately apparent. Like theoretical yield, percent yield is useful in many fields, including agriculture, the food industry, the pharmaceutical industry, and environmental science.

Similarities Between Theoretical Yield and Percent Yield

• Both theoretical yield and percent yield help to assess the result of a chemical reaction
• Moreover, they are essential for quality control in chemical processes.

Difference Between Theoretical Yield and Percent Yield

Definition

The theoretical yield is the calculated maximum amount of product that can be obtained from a chemical reaction, assuming that the reaction proceeds to completion without any losses or inefficiencies. Percent yield is a measure of the actual efficiency of a chemical reaction, expressed as a percentage, comparing the actual yield of a reaction to the theoretical yield and quantifying how much of the expected product was obtained in a real-world scenario.

Calculation

The theoretical yield is typically expressed in units of mass (e.g., grams), moles, or volume, depending on the nature of the reactants and products involved in the reaction. But percent yield is expressed as a percentage (%).

Nature

Theoretical yield assumes ideal conditions, where the reaction proceeds with complete conversion of reactants into products, and there are no impurities, side reactions, or losses. However, percent yield provides a practical measure of a reaction’s efficiency under real-world conditions, taking into account factors that can affect the actual yield.

FAQ: Theoretical Yield and Percent Yield

Is percent yield always 100 percent?

• No, but if the theoretical yield and actual yield are the same, then the percent yield is 100 percent.

Why percent yield is not always 100 percent?

• Percent yield is not always 100 percent because real-world chemical reactions are subject to various factors that can reduce efficiency. These factors include impurities, incomplete reactions, side reactions, and losses during the experimental process.

What is the relationship between percentage yield and theoretical yield of synthesized product?

• The relationship between percentage yield and theoretical yield is expressed through the formula:

Percentage yield compares the actual yield obtained in a real-world experiment to the theoretical yield. It provides a measure of the efficiency of a chemical reaction.

Conclusion

The main difference between theoretical yield and percent yield is that theoretical yield is the maximum amount of product that can be obtained from a chemical reaction, assuming that the reaction proceeds to completion and all reactants are converted into products without any loss, whereas percent yield is a measure of the efficiency of a chemical reaction in the laboratory.

Reference:

1. “Finding Theoratical Yield. ” Byju’s.

Image Courtesy:

1. “Conversion, Selectivity and Yield” By IJMacD – Own work (Public Domain) via Commons Wikimedia