Actual yield refers to the amount of product that is truly obtained when a chemical reaction is carried out in a laboratory or industrial setting. It can be found primarily through experimental measurement or, in certain contexts, calculated if the percent yield and theoretical yield are already known.
What is Actual Yield?
The actual yield is the quantity of product that is physically recovered from a chemical reaction. Unlike theoretical yield, which is an ideal calculation, the actual yield is a real-world, experimentally determined value. It is almost always less than the theoretical yield due to various factors such as incomplete reactions, side reactions, purification losses, or transfer errors.
To learn more, you can read about actual yield on Britannica.
Methods to Determine Actual Yield
There are two primary ways to determine actual yield: through direct experimental measurement or by calculation using related yield concepts.
1. Experimental Measurement (Primary Method)
The most direct and fundamental way to find actual yield is by performing the chemical reaction and then carefully measuring the amount of product formed. This typically involves:
- Performing the Reaction: Carrying out the chemical synthesis according to a specific procedure.
- Isolation: Separating the desired product from unreacted starting materials, byproducts, and solvents. This may involve techniques like filtration, distillation, decantation, or extraction.
- Purification: Removing impurities from the isolated product to obtain it in a pure form. This can include recrystallization, chromatography, or washing.
- Drying: Ensuring the product is free of residual solvents, which would artificially increase its measured mass.
- Weighing: Accurately measuring the mass or volume of the pure, dry product using appropriate laboratory equipment (e.g., analytical balance).
This measured quantity is the actual yield.
2. Calculation Using Percent Yield and Theoretical Yield (Secondary Method)
While actual yield is fundamentally an experimental value, it can be calculated if you know the percent yield and the theoretical yield of a reaction. This method is often used to:
- Predict the expected actual yield of a known reaction with an established percent yield.
- Verify experimental results or determine consistency across different runs.
The formula for calculating actual yield in this scenario is straightforward:
Actual Yield = (Percent Yield / 100) × Theoretical Yield
This formula rearranges the definition of percent yield to solve for the actual yield. For example, if a reaction typically has an 80% yield, you would multiply the theoretical yield by 0.80 to find the expected actual yield.
Understanding Key Terms
To apply the calculation method effectively, it's crucial to understand the other types of yield:
Theoretical Yield
The theoretical yield is the maximum amount of product that can be formed from a given amount of reactants, assuming the reaction goes to completion without any losses. It is calculated using stoichiometry (the quantitative relationships between reactants and products in a balanced chemical equation) and the concept of a limiting reactant.
Explore more about theoretical yield to understand its calculation.
Percent Yield
The percent yield is a measure of the efficiency of a chemical reaction. It compares the actual yield to the theoretical yield and is expressed as a percentage.
Percent Yield = (Actual Yield / Theoretical Yield) × 100%
Learn more about percent yield and its significance.
Example Calculation
Let's say you are performing a reaction that, based on previous experiments, has a typical percent yield of 75%. You have calculated your theoretical yield for the current batch to be 10.0 grams.
To find the expected actual yield:
- Convert percent yield to a decimal:
75% / 100 = 0.75 - Multiply by the theoretical yield:
Actual Yield = 0.75 × 10.0 grams
Actual Yield = 7.5 grams
So, the expected actual yield for this reaction under these conditions would be 7.5 grams.
Table Summary of Yield Types
| Yield Type | Definition | How It's Found/Calculated |
|---|---|---|
| Actual Yield | The amount of product experimentally obtained from a reaction. | Measured directly in the lab (weighing) or calculated from Percent Yield and Theoretical Yield: (Percent Yield / 100) × Theoretical Yield |
| Theoretical Yield | The maximum amount of product that could be formed based on stoichiometry. | Calculated from the balanced chemical equation and limiting reactant. |
| Percent Yield | The ratio of actual yield to theoretical yield, expressed as a percentage. | Calculated by: (Actual Yield / Theoretical Yield) × 100% |
Importance of Actual Yield
Understanding actual yield is critical in various fields, especially chemistry, pharmaceuticals, and manufacturing. It helps:
- Assess Reaction Efficiency: A low actual yield indicates inefficiencies in the reaction or purification process, prompting optimization.
- Predict Production Output: In industrial settings, knowing the expected actual yield allows for accurate production planning and resource allocation.
- Evaluate Experimental Skill: For students, achieving a high actual yield often reflects careful experimental technique.
- Determine Cost-Effectiveness: For commercial processes, a higher actual yield means less waste and more product per unit of raw material, leading to lower production costs.
