Limiting Reactants and Percent Yield

Mr. Anderson explains limiting reactants and percent yield in chemical reactions. He uses a cookie recipe analogy to introduce the concept of limiting reactants, followed by examples of hydrogen and methane combustion. The video details how to calculate limiting reactants using moles and mass, and concludes with an explanation of percent yield, highlighting the difference between predicted and actual yields.

What is a limiting reactant in a chemical reaction?

• A catalyst that speeds up the reaction

• A product that is formed in the reaction

• A reactant that determines the amount of product formed

• A reactant that is in excess

In the hydrogen combustion example, which reactant was limiting?

• Carbon dioxide

• Water

• Hydrogen gas

• Oxygen gas

During the combustion of methane, what is left over after the reaction?

• Water

• Carbon dioxide

• Methane

• Oxygen

Why can't we determine the limiting reactant by just looking at the mass of reactants?

• Because mass does not account for the number of moles

• Because mass is not related to chemical reactions

• Because mass is always conserved

• Because mass is irrelevant in chemistry

What is the first step in determining the limiting reactant in a chemical reaction?

• Compare the masses

• Convert grams to moles

• Calculate the percent yield

• Identify the products

How is percent yield calculated in a chemical reaction?

• By dividing the predicted yield by the actual yield

• By dividing the actual yield by the predicted yield

• By multiplying the actual yield by the predicted yield

• By subtracting the predicted yield from the actual yield

Why is the percent yield never 100% in a chemical reaction?

• Because the products are always impure

• Because the reaction is always incomplete

• Because not all molecules react perfectly

• Because some reactants are always left over