What is Percent Yield?
Percent yield measures the efficiency of a chemical reaction by comparing how much product was actually obtained to how much could theoretically be produced. It is a key metric in chemistry for evaluating reaction success.
How to Calculate Percent Yield
The formula is:
[\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100]
Where:
- Actual Yield is the amount of product you actually obtained
- Theoretical Yield is the maximum amount possible based on stoichiometry
Calculation Example
If a reaction theoretically should produce 50 grams of product but you only obtained 42 grams:
[\text{Percent Yield} = \frac{42}{50} \times 100 = 84%]
This indicates an 84% efficient reaction.
Reasons for Low Yield
- Incomplete Reactions: Not all reactants converted to products
- Side Reactions: Some reactants formed unwanted products
- Loss During Transfer: Product lost when moving between containers
- Purification Losses: Product lost during filtration, drying, or other purification steps
- Equilibrium Limitations: Reversible reactions may not go to completion
Improving Percent Yield
- Use excess of inexpensive reagents
- Optimize reaction conditions (temperature, time, catalysts)
- Minimize transfer steps
- Use efficient purification techniques
- Ensure reactions go to completion