5.4.2 Limiting Reagents

• What is a limiting reagent in a chemical reaction?

  The reactant used up first
• The limiting reagent determines the amount of product
• Steps to identify the limiting reagent in a reaction

  1️⃣ Convert the mass of each reactant to moles using the molar mass

  2️⃣ Divide the number of moles of each reactant by its stoichiometric coefficient

  3️⃣ The reactant with the smallest result is the limiting reagent
• The limiting reagent is always present in the largest amount.

  False
• What happens to the limiting reagent during a reaction?

  It is fully consumed
• The excess reagent is present in a larger amount.
• Understanding the limiting reagent is crucial for optimizing chemical reactions.
• What is the first step in identifying the limiting reagent in a chemical reaction?

  Convert mass to moles
• Match the key concepts with their definitions:

  Limiting Reagent ↔️ Reactant used up completely first

  Stoichiometric Coefficient ↔️ Indicates moles needed for reaction
• The reactant with the smallest ratio after division is the limiting
• The limiting reagent determines the maximum theoretical yield of the product.
• Why is identifying the limiting reagent important for predicting product yield?

  It sets the maximum amount
• Steps to optimize a chemical reaction using the limiting reagent

  1️⃣ Identify the limiting reagent

  2️⃣ Adjust reaction conditions to use excess reagents efficiently

  3️⃣ Avoid waste of reactants
• The limiting reagent helps predict the theoretical yield of the reaction.
• What is the limiting reagent in a chemical reaction?

  The reactant fully consumed first
• The limiting reagent allows you to accurately predict the theoretical yield
• Knowing the limiting reagent helps optimize reactions to avoid waste of excess reagents.
• What is the relative amount of a limiting reagent compared to an excess reagent in a chemical reaction?

  Smaller
• The excess reagent is partially consumed, and some remains after the reaction
• The excess reagent determines the product yield in a reaction.

  False
• Steps to identify the limiting reagent in a reaction

  1️⃣ Convert the mass of each reactant to moles using its molar mass.

  2️⃣ Divide the moles of each reactant by its stoichiometric coefficient in the balanced equation.

  3️⃣ The reactant with the smallest result is the limiting reagent.
• In the reaction 2H2 + O2 → 2H2O, what are the moles of H2 if you start with 4g of H2 (molar mass = 2 g/mol)?

  2 moles
• For the reaction 2H2 + O2 → 2H2O, the moles of O2 from 32g of O2 (molar mass = 32 g/mol) is 1
• In the reaction 2H2 + O2 → 2H2O, if the ratios of H2 and O2 are both 1, neither reactant is in excess.
• What is the definition of a limiting reagent?

  Reactant fully used up
• Match the concept with its definition:

  Limiting Reagent ↔️ Reactant fully used up

  Stoichiometric Coefficient ↔️ Number preceding a reactant
• What is the first step to calculate the amount of product formed from a limiting reagent?

  Identify the limiting reagent
• The moles of the limiting reagent are used to determine the maximum amount of product
• In the reaction 2H2 + O2 → 2H2O, if you have 4 moles of H2 and 1 mole of O2, O2 is the limiting reagent.
• In the reaction 2H2 + O2 → 2H2O, if O2 is the limiting reagent and you started with 1 mole, how many moles of H2O can be formed?

  2 moles
• Steps to determine the remaining amount of the excess reactant

  1️⃣ Determine the limiting reagent.

  2️⃣ Use the stoichiometric ratio to find the moles of the excess reactant needed to react with the limiting reagent.

  3️⃣ Subtract the moles used from the initial moles to find the moles remaining.

  4️⃣ Convert the moles remaining to mass if required.
• In the reaction 2H2 + O2 → 2H2O, if O2 is the limiting reagent and you started with 4 moles of H2, how many moles of H2 are needed to react with 1 mole of O2?

  2 moles
• For the reaction 2H2 + O2 → 2H2O, if you started with 4 moles of H2 and O2 is the limiting reagent, the moles of H2 remaining is 2
• In the reaction 2H2 + O2 → 2H2O, if 2 moles of H2 remain, the mass of H2 remaining is 4g.
• In the reaction 2H2 + O2 → 2H2O, what is the limiting reagent if you start with 4 moles of H2 and 1 mole of O2?

  O2
• If 4 moles of H2 react with 1 mole of O2 in the reaction 2H2 + O2 → 2H2O, the remaining moles of H2 are 2
• What is the excess reactant in a chemical reaction?

  The reactant that remains
• Steps to calculate the remaining amount of the excess reactant:

  1️⃣ Determine the limiting reagent

  2️⃣ Use the stoichiometric ratio to find the moles of the excess reactant needed

  3️⃣ Subtract the moles used from the initial moles to find the moles remaining

  4️⃣ Convert the moles remaining to mass if required
• A limiting reagent determines the amount of product that can be formed in a chemical reaction.
• In terms of amount, is a limiting reagent present in a smaller or larger amount compared to an excess reagent?

  Smaller