Limiting Reagents and Stoichiometry

What is stoichiometry primarily concerned with?

• The color changes in reactions

• The relationship between chemical quantities in reactions

• The energy changes in reactions

• The speed of chemical reactions

What is a limiting reagent in a chemical reaction?

• The reactant that is in excess

• The reactant that runs out first

• The catalyst used in the reaction

• The product formed in the largest amount

How can you identify a limiting reagent problem?

• By the speed of the reaction

• By the color of the reactants

• By the temperature of the reaction

• By being given amounts of two reactants

In a reaction between aluminum and iron oxide, how many moles of aluminum are needed to react with 10 moles of iron oxide?

• 5 moles

• 6.67 moles

• 10 moles

• 20 moles

When given 27 grams of copper, how many grams of chromium are needed to react completely?

• 25 grams

• 10.5 grams

• 14.6 grams

• 20 grams

What is the percent yield if the actual yield is 38.1 grams and the theoretical yield is 42 grams?

• 95%

• 80%

• 85%

• 90%

How do you calculate the percent yield of a reaction?

• Add the actual yield to the theoretical yield

• Subtract the actual yield from the theoretical yield

• Divide the actual yield by the theoretical yield and multiply by 100

• Divide the theoretical yield by the actual yield and multiply by 100

In a limiting reagent problem, what determines the maximum amount of product that can be formed?

• The reactant in excess

• The reactant that is completely used up

• The catalyst used

• The fastest reacting substance

If 72.9 grams of iron sulfide react with 79.8 grams of hydrochloric acid, how many grams of the excess reactant are left over?

• 25.4 grams

• 20.2 grams

• 15.3 grams

• 10.2 grams

What is the first step in solving a stoichiometry problem involving grams?

• Convert grams to liters

• Write a balanced chemical equation

• Calculate the percent yield

• Determine the color of the reactants