what are some factors that may cause a percent yield to be greater than 100% ? what are some that may cause it to be less?
more than 100 in a lab? Usually measurement errors.
Less than 100 percent? Measurement errors, some of the product is washed away in solution, or the reaction did not react the way one thought (I remember Mg burning in air, then measuring MgO to get yeild. Problem is, some of the Mg formed Mg3N2 with the air.
Percent yield is a calculation used in chemistry to determine how much product is obtained compared to the maximum possible yield. A percent yield greater than 100% suggests that the actual yield of the reaction is higher than the theoretical yield, which is usually not possible. On the other hand, a percent yield less than 100% indicates that the actual yield is lower than the theoretical yield.
Factors that may cause a percent yield to be greater than 100% include:
1. Impurities in reactants: If the starting materials contain impurities, the measured yield may appear higher due to additional mass contributions from these impurities. This can artificially inflate the percent yield.
Factors that may cause a percent yield to be less than 100% include:
1. Incomplete reactions: Sometimes, the reactants do not fully convert into products due to factors such as insufficient time, incomplete mixing, or unfavorable reaction conditions. In these cases, the actual yield will be lower than the theoretical yield.
2. Side reactions: In some cases, unwanted side reactions can occur, leading to the formation of products different from the desired product. These side reactions reduce the overall yield.
3. Losses during separation or purification: During the separation or purification processes, some of the product can be lost. For example, if the product is not completely transferred during filtration or if it sticks to the container, the measured yield will be lower than the expected yield.
4. Human error: Errors made during the experiment, such as inaccurate measurements or improper techniques, can result in lower yields. It is vital to carefully follow the experimental procedure to minimize these errors.
To determine the percent yield, you need to know the actual yield of the reaction and the theoretical yield, which is the maximum amount of product that can be obtained based on stoichiometry. The percent yield is calculated using the following equation:
Percent Yield = (Actual Yield / Theoretical Yield) * 100
You can calculate the theoretical yield by using stoichiometry, where the balanced chemical equation provides the molar ratios between reactants and products. To get the actual yield, experimental techniques such as weighing, titration, or spectroscopy are utilized to measure the amount of product obtained.
By comparing the actual and theoretical yields, you can calculate the percent yield and assess the efficiency of the reaction.