Theoretical Yield and Limiting Reactants

This video tutorial covers the concepts of limiting reactant and percent yield, which are essential in stoichiometry. The instructor uses the metaphor of making sandwiches to explain how one reactant limits the amount of product formed. Two example problems are solved: one involving the production of urea from ammonia and carbon dioxide, and another involving the precipitation of lead chloride from potassium chloride and lead nitrate. The video demonstrates how to calculate theoretical yield and percent yield, emphasizing the importance of identifying the limiting reactant.

What is the main concept introduced using the sandwich metaphor?

• The concept of a limiting reactant in chemistry

• The nutritional value of sandwiches

• How to make a perfect sandwich

• The importance of bread in making sandwiches

In the urea production problem, what is the first step to determine the limiting reactant?

• Calculate the molar mass of urea

• Measure the temperature of the reaction

• Choose one reactant and calculate the amount of product it can produce

• Mix the reactants in a beaker

Why is it important to calculate the theoretical yield in a chemical reaction?

• To measure the temperature change during the reaction

• To predict the maximum amount of product that can be formed

• To determine the exact amount of reactants needed

• To find out the cost of the reaction

What does a percent yield of less than 100% indicate?

• The reaction produced more product than expected

• The actual yield was less than the theoretical yield

• There were no errors in the experiment

• The reaction was performed perfectly

In the lead chloride problem, what is the significance of determining the limiting reactant?

• It helps in identifying the excess reactant

• It determines the color of the product

• It is used to calculate the temperature of the reaction

• It is not important for the reaction

What is the theoretical yield of lead chloride in the second problem?

• 2.000 grams

• 1.000 grams

• 1.530 grams

• 1.276 grams

How is the percent yield calculated in a chemical reaction?

• By dividing the theoretical yield by the actual yield

• By multiplying the actual yield by the theoretical yield

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

• By adding the actual yield to the theoretical yield

What does a percent yield of 88.9% suggest about the lead chloride reaction?

• The reaction was highly efficient

• The reaction was inefficient

• The reaction produced more product than expected

• The reaction did not occur

Why might the actual yield be lower than the theoretical yield in a lab experiment?

• Due to the high temperature of the reaction

• Because the reactants were not mixed

• Because the theoretical yield is always incorrect

• Due to measurement errors or incomplete reactions

What is the purpose of using stoichiometry in chemical reactions?

• To find the pH of the solution

• To measure the temperature change

• To calculate the amounts of reactants and products

• To determine the color of the reactants