5.4.2 Limiting Reagents

• What is stoichiometry the quantitative relationship between?

  Reactants and products
• Stoichiometry helps predict the masses or volumes
• Stoichiometry involves determining the exact amounts of substances involved in a reaction using balanced chemical equations.
• In the reaction $2H_{2} +$$O_{2} \rightarrow 2H_{2}O$, what is the stoichiometric ratio between hydrogen and water?


  2:2
• Chemical equations use chemical formulas
• A balanced chemical equation ensures the number of atoms of each element is equal on both sides.
• Balance the equation for methane reacting with oxygen:$CH_{4} +$$O_{2} \rightarrow CO_{2} +$$H_{2}O$


  $CH_{4} +$$2O_{2} \rightarrow CO_{2} +$$2H_{2}O$
• Limiting reagents are reactants that are completely consumed
• The limiting reagent determines the maximum yield of a reaction.
• What law is followed when balancing chemical equations?

  Law of Conservation of Mass
• In the balanced equation $CH_{4} +$$2O_{2} \rightarrow CO_{2} +$$2H_{2}O$, the stoichiometric ratio between oxygen and water is 2:2
• Limiting reagents are reactants that are completely consumed during a chemical reaction, limiting the amount of product
• In the reaction2H_{2} + O_{2} \rightarrow 2H_{2}O</latex>, if 4 moles of $H_{2}$ react with 1 mole of $O_{2}$, which is the limiting reagent?


  $O_{2}$
• The limiting reagent is the reactant that is left over after a reaction is completed.

  False
• Match the term with its definition:

  Limiting Reagent ↔️ Reactant completely consumed

  Excess Reagent ↔️ Reactant left over
• To identify a limiting reagent, first write the balanced chemical equation.
• Steps to identify a limiting reagent in a reaction:

  1️⃣ Write the balanced chemical equation

  2️⃣ Convert reactant masses to moles

  3️⃣ Calculate the mole ratio

  4️⃣ Determine which reactant is completely consumed first
• What is the first step to calculate the amount of product formed using the limiting reagent?

  Identify the limiting reagent
• The balanced chemical equation is used to find the mole ratio between the limiting reagent and the product.
• Calculate the moles of product formed by multiplying the moles of the limiting reagent by the mole ratio
• What is stoichiometry?

  Quantitative relationship in reactions
• How are the moles of product calculated using the limiting reagent in stoichiometry?

  Multiply by mole ratio
• If $O_{2}$ is the limiting reagent with 1 mole in the reaction $2H_{2} +$$O_{2} \rightarrow 2H_{2}O$, 2 moles of $H_{2}O$ are formed.
• The limiting reagent ensures that calculations are based on the reactant that is completely consumed
• What is stoichiometry defined as in chemistry?

  Quantitative relationships
• How are chemical reactions represented in chemistry?

  Chemical equations
• A balanced chemical equation ensures the number of atoms of each element is equal on both sides.
• What is the balanced equation for CH_{4} + O_{2} \rightarrow CO_{2} + H_{2}O</latex>?

  $CH_{4} +$$2O_{2} \rightarrow CO_{2} +$$2H_{2}O$
• What is the role of limiting reagents in a chemical reaction?

  Control maximum yield
• In the reaction $2H_{2} +$$O_{2} \rightarrow 2H_{2}O$, if 4 moles of $H_{2}$ react with 1 mole of $O_{2}$, $O_{2}$ is the limiting reagent
• The concept of limiting reagents aligns with stoichiometry in chemical reactions.
• Steps to identify limiting reagents in a chemical reaction

  1️⃣ Write the balanced chemical equation

  2️⃣ Convert reactant masses to moles

  3️⃣ Calculate the mole ratio

  4️⃣ Determine which reactant is completely consumed first
• What must be determined after calculating the mole ratio to identify the limiting reagent?

  Reactant completely consumed
• For the reaction 2H_{2} + O_{2} \rightarrow 2H_{2}O</latex>, if 4 moles of $H_{2}$ react with 1 mole of $O_{2}$, $O_{2}$ is the limiting reagent.
• To calculate the amount of product formed, the first step is to identify the limiting reagent
• What are excess reagents in a chemical reaction?

  Reactants in excess
• In $2H_{2} +$$O_{2} \rightarrow 2H_{2}O$, if 4 moles of H_{2}</latex> react with 1 mole of $O_{2}$, $H_{2}$ is the excess reagent.
• To solve stoichiometry problems involving limiting reagents, the first step is to write the balanced chemical equation
• In the reaction $N_{2}(g) +$$3H_{2}(g) \rightarrow 2NH_{3}(g)$, if 28 grams of $N_{2}$ react with 12 grams of $H_{2}$, which is the limiting reagent?


  $N_{2}$
• In the reaction $N_{2}(g) +$$3H_{2}(g) \rightarrow 2NH_{3}(g)$, 2 moles of $NH_{3}$ are formed if 1 mole of $N_{2}$ is the limiting reagent.