Theoretical Yield and Percent Yield

This video tutorial explains the concept of percent yield in chemistry, which measures the efficiency of a chemical reaction by comparing the actual yield obtained in a lab to the theoretical yield predicted by stoichiometry. The tutorial provides a step-by-step example of calculating percent yield, including balancing a chemical equation, determining the theoretical yield, and using the percent yield formula. The example involves reacting aluminum with hydrochloric acid to produce hydrogen gas, and the tutorial emphasizes the importance of using moles instead of grams in calculations.

What is the primary purpose of calculating percent yield in a chemical reaction?

• To calculate the cost of reactants

• To measure the temperature change during the reaction

• To compare the actual product obtained with the theoretical prediction

• To determine the speed of the reaction

Which of the following best describes the 'actual yield' in a chemical reaction?

• The amount of reactant used in the reaction

• The amount of product predicted by theory

• The amount of product actually obtained from the experiment

• The total mass of all reactants

In the example problem, what is the first step in determining the theoretical yield of hydrogen?

• Calculating the percent yield

• Measuring the temperature of the reaction

• Balancing the chemical equation

• Determining the cost of reactants

What is the significance of balancing the chemical equation in the context of this problem?

• It helps in determining the speed of the reaction

• It ensures the correct stoichiometric ratios are used

• It is necessary for measuring temperature changes

• It is required for calculating the cost of reactants

Why can't grams be directly used in a BCA table for stoichiometry calculations?

• Because grams are not a unit of time

• Because grams do not indicate the number of particles

• Because grams are not a unit of volume

• Because grams are not a unit of temperature

What is the molar mass of hydrogen gas (H2) used in the calculations?

• 1 gram per mole

• 3 grams per mole

• 2 grams per mole

• 4 grams per mole

What is the ratio of aluminum to hydrogen in the balanced chemical equation used in the example?

• 1:1

• 2:3

• 3:2

• 1:2

How is the percent yield calculated once the actual and theoretical yields are known?

• By adding the actual and theoretical yields together

• By dividing the actual yield by the theoretical yield and multiplying by 100

• By subtracting the actual yield from the theoretical yield

• By dividing the theoretical yield by the actual yield and multiplying by 100

If the theoretical yield of hydrogen is 0.555 grams and the actual yield is 0.525 grams, what is the percent yield?

• 90%

• 85%

• 100%

• 95%

What does a percent yield of 95% indicate about the experiment?

• The actual yield was very close to the theoretical yield

• The actual yield was much lower than expected

• The experiment was not successful

• The theoretical yield was overestimated