Give three possible sources of error in this experiment that would lead to a percent yield other than 100%. Clearly indicate whether each error would result in a higher or lower value and explain why that would be the result.
The Correct Answer and Explanation is :
In an experiment measuring percent yield, several sources of error can lead to a result that deviates from the theoretical yield of 100%. Here are three possible errors, along with explanations of how each would affect the result:
1. Incomplete Reaction (Lower Percent Yield)
- Error Explanation: If the reaction does not go to completion, it means that some of the reactants remain unreacted, leaving less product than theoretically expected. For instance, if a chemical reaction reaches an equilibrium before all the reactants are converted to products, the amount of product collected will be lower than the expected yield.
- Effect on Percent Yield: This error would result in a lower percent yield. The actual yield would be less than the theoretical yield, leading to a calculated percent yield of less than 100%.
2. Loss of Product During Filtration or Handling (Lower Percent Yield)
- Error Explanation: When isolating and purifying the product, some may be lost due to incomplete transfer, spillage, or loss during filtration, washing, or drying. This is especially common with solid products, where some material may remain on the filter paper or be lost during the transfer between containers.
- Effect on Percent Yield: The result would be a lower percent yield because the actual amount of product collected is less than what was expected based on the theoretical calculations. Even a small amount of loss during handling can lead to a significant decrease in the yield.
3. Impure Reactants (Lower or Higher Percent Yield, Depending on the Impurity)
- Error Explanation: If the reactants used are impure, the actual amount of the active reagent may be less than assumed. For example, if a reactant contains a significant amount of moisture or other impurities, the amount of substance available to react would be less, possibly leading to a lower theoretical yield. Alternatively, an impurity in the reactants may introduce side reactions that produce additional products, potentially increasing the actual yield.
- Effect on Percent Yield: The effect can be either an increase or decrease in percent yield. If the impurity consumes reagents or prevents full reaction, the yield may be lower. If the impurity contributes to side reactions, it could increase the amount of product formed, giving a yield higher than expected.
Conclusion:
Errors in an experiment can lead to either higher or lower percent yields, depending on the nature of the issue. Common causes of lower percent yield include incomplete reactions and product loss, while impure reactants can sometimes cause unexpected results. Proper handling, careful measurements, and ensuring complete reactions are critical to obtaining accurate yield measurements.