How to Calculate Percent Yield

Summary

This video tutorial teaches how to calculate percent yield in chemical reactions. It explains the difference between actual yield (the amount obtained in the lab) and theoretical yield (calculated using stoichiometry), and provides clear step-by-step examples to illustrate the process. Viewers will learn to calculate percent yield using the formula: (Actual Yield / Theoretical Yield) x 100%. The tutorial also covers how to determine theoretical yield when percent yield is given, as well as how to calculate the actual yield from known percent yield. This helps assess the efficiency and accuracy of chemical reactions in the laboratory.

Takeaways

• 😀 Percent yield is a comparison between the actual yield (what you obtain in the lab) and the theoretical yield (what you should obtain from stoichiometry).
• 😀 The actual yield is the amount of product you get from performing the chemical reaction in the laboratory.
• 😀 The theoretical yield is determined through stoichiometry based on the balanced chemical equation and initial reactants.
• 😀 Percent yield is calculated using the formula: (Actual Yield / Theoretical Yield) × 100%.
• 😀 In an ideal reaction, the percent yield should be 100%, but real-life reactions often result in less product due to errors.
• 😀 Limiting reactants determine the theoretical yield, and stoichiometry helps calculate the maximum amount of product that can be made.
• 😀 An example calculation showed that a percent yield of 97.6% was achieved when 200.2 g of sodium chloride was obtained from a theoretical yield of 205 g.
• 😀 Percent yield reflects how efficiently a reaction was conducted, with deviations often due to human or instrumental errors.
• 😀 If the actual yield and percent yield are known, the theoretical yield can be calculated by rearranging the percent yield formula.
• 😀 The process of calculating theoretical yield includes converting mass to moles, applying the mole ratio, and then converting back to mass using the molar mass of the product.
• 😀 Understanding percent yield allows chemists to assess the quality of experimental results and troubleshoot factors that may have caused discrepancies.

Q & A

What is percent yield and how is it calculated?

Percent yield is a comparison between the actual yield (the amount of product obtained in the experiment) and the theoretical yield (the amount of product predicted by stoichiometry). It is calculated using the formula: Percent Yield = (Actual Yield / Theoretical Yield) × 100%.

What is the difference between actual yield and theoretical yield?

The actual yield is the amount of product obtained in a laboratory experiment, whereas the theoretical yield is the amount of product that should be produced according to stoichiometry calculations, assuming perfect conditions.

In the example with sodium peroxide and water, what was the actual yield?

In the example with sodium peroxide and water, the actual yield was 19.1 grams of sodium hydroxide.

How do you calculate percent yield using the formula?

To calculate percent yield, divide the actual yield by the theoretical yield, then multiply the result by 100%. For example, if the actual yield is 19.1 grams and the theoretical yield is 21.2 grams, the percent yield is (19.1 / 21.2) × 100% = 90.0%.

Why might the actual yield be lower than the theoretical yield?

The actual yield may be lower than the theoretical yield due to factors such as human error, instrument inaccuracies, incomplete reactions, or loss of product during the experiment.

What does a percent yield of 90% indicate in the example with sodium hydroxide?

A percent yield of 90% indicates that the amount of sodium hydroxide produced in the lab was 10% less than what was expected based on stoichiometry, which could be due to errors or inefficiencies in the experimental process.

What does it mean if the theoretical yield is higher than the actual yield?

If the theoretical yield is higher than the actual yield, it suggests that the experiment did not go perfectly as expected, and some factors (like reaction efficiency or product loss) caused a lower output.

In the example with potassium and aluminum oxide, what is the role of percent yield?

In the potassium and aluminum oxide example, percent yield is used to determine the actual amount of potassium oxide produced in the lab, given the theoretical yield and the provided percent yield of 92.5%.

How can you calculate the theoretical yield when you know the actual yield and percent yield?

To calculate the theoretical yield when you know the actual yield and percent yield, use the formula: Theoretical Yield = (Actual Yield × 100%) / Percent Yield. For example, if the actual yield is 275 grams and the percent yield is 97%, the theoretical yield would be (275 × 100%) / 97% = 284 grams.

What factors could affect the accuracy of percent yield in a chemical experiment?

Factors that could affect the accuracy of percent yield include human errors (e.g., miscalculations or incorrect measurements), impurities in reactants, incomplete reactions, losses during product transfer, or limitations in lab equipment.