3.1.3 Understanding and identifying limiting reactants

• What does a mole ratio indicate in a chemical reaction?

  It shows the moles of reactants needed
• What is a limiting reactant in a chemical reaction?

  The ingredient that gets used up first
• What does a balanced chemical equation represent?

  The mole ratio of reactants
• In the reaction of nitrogen and hydrogen, how many moles of ammonia are produced from 1 mole of nitrogen and 3 moles of hydrogen?

  2 moles of ammonia
• How do you use mole ratios to find the limiting reactant in a reaction?

  • Use a balanced chemical equation.
  • Identify stoichiometric coefficients.
  • Calculate actual moles divided by coefficients.
  • The smallest ratio indicates the limiting reactant.
• If you have 4 moles of hydrogen and 3 moles of oxygen, how do you determine the limiting reactant?

  Calculate the ratios of each reactant
• What indicates the limiting reactant in a chemical reaction?

  The reactant with the smallest ratio
• How do you convert moles of product to mass?

  Use $Mass (g) =$$Moles \times Molar Mass (g / mol)$
• How do you convert mass of a limiting reactant to moles?

  Use $Moles =$$\frac{Mass (g)}{Molar Mass (g / mol)}$
• Why is the theoretical yield important in chemistry?

  It indicates the maximum possible product
• How many oxygen atoms are shown in the reactants?

  2
• What is the process shown in the image?

  The image depicts the chemical reaction of hydrogen and oxygen to form water.
• How does the number of hydrogen and oxygen atoms change from the reactants to the products?

  The number of hydrogen atoms doubles and the number of oxygen atoms remains the same
• What are the chemical symbols for hydrogen and oxygen shown in the image?

  • Hydrogen (H)
  • Oxygen (O)
• What is the mole ratio of hydrogen to water in the reaction?

  • The mole ratio is 2:1
  • For every 2 moles of hydrogen, 1 mole of water is formed
• What is the balanced chemical equation for the reaction shown in the image?

  2H₂ + O₂ → 2H₂O
• What is the first step to identify the limiting reactant in a chemical reaction?

  Start with a balanced equation
• What is the first step in calculating theoretical yield?

  Identify the limiting reactant
• What is the theoretical yield in a chemical reaction?

  Maximum product from a reaction
• What are the reactants and products of the reaction shown in the image?

  Reactants:

  • Hydrogen (H₂)
  • Oxygen (O₂)

  
  

  Product:

  • Water (H₂O)
• How many grams of H₂O are produced from 4g of H₂?

  36 grams
• What is the first step to solve problems involving limiting reactants?

  Use the mole ratio from the balanced equation
• What are the steps to identify the limiting reactant using mole ratios?

  1. Start with a balanced equation.
  2. Determine the mole ratio from the equation.
  3. Calculate the ratio for each reactant.
  4. Identify the limiting reactant by comparing ratios.
• What are the steps to calculate theoretical yield?

  1. Identify the limiting reactant
  2. Convert mass of limiting reactant to moles
  3. Use mole ratio to find moles of product
  4. Convert moles of product to mass
• What is the mole ratio of nitrogen to hydrogen in the given reaction?

  • Mole ratio of $N_{2} : H_{2}$ is $1 : 3$
  • Indicates 1 mole of nitrogen reacts with 3 moles of hydrogen
• Why is it essential to use balanced chemical equations for mole ratios?

  They provide accurate stoichiometric coefficients
• How does the mole ratio help in identifying the limiting reactant?

  It shows the proportion of reactants needed
• What is the definition of a limiting reactant?

  A reactant that controls product formation
• If you have one egg and plenty of flour and sugar, what is the limiting reactant when baking a cake?

  The egg
• What are the steps to identify the limiting reactant?

  1. Divide the amount of each reactant by its mole ratio.
  2. Compare the values obtained.
  3. The smallest value indicates the limiting reactant.
• What is the mole ratio used for in theoretical yield calculations?

  To find moles of product from reactants
• How many hydrogen atoms are shown in the reactants?

  8
• In the reaction $2H_{2} +$$O_{2} \rightarrow 2H_{2}O$, how many moles of hydrogen react with one mole of oxygen?


  Two moles of hydrogen
• How do you find the limiting reactant?

  Find the reactant that runs out first
• How does a limiting reactant affect product formation?

  It controls how much product can be made
• What is the purpose of applying mole ratios in a chemical reaction?

  To find the limiting reactant
• What happens to the reaction when all hydrogen is used up in the presence of excess oxygen?

  The reaction stops despite excess oxygen
• What does the balanced equation $N_{2} +$$3H_{2} \rightarrow 2NH_{3}$ indicate about the reactants?


  Both reactants are consumed in exact proportion
• What is the purpose of finding the limiting reactant?

  To determine which reactant is consumed first
• How do you calculate the ratio for each reactant?

  Divide actual moles by stoichiometric coefficients