Limiting reactants

• What are limiting reactants?

  Reactants that determine the amount of product
• What happens when hydrochloric acid reacts with calcium carbonate?

  Produces calcium chloride, water, and carbon dioxide
• How can you tell a reaction is taking place between hydrochloric acid and calcium carbonate?

  Solid calcium carbonate disappears and gas bubbles form
• What indicates that one reactant has been completely used up in a reaction?

  The reaction stops and no more fizzing occurs
• What is a limiting reactant in a chemical reaction?

  The reactant that limits product formation
• What is the term for a reactant that is not completely used up?

  Excess reactant
• Why is it important to identify the limiting reactant?

  It determines the amount of product formed
• What happens if more calcium carbonate is added to the reaction?

  More fizzing occurs until calcium carbonate is used up
• What is combustion in the context of sodium burning in air?

  It means reacting with oxygen in the air
• What is the first step in calculating the mass of sodium oxide produced?

  Write and balance the chemical equation
• How do you calculate the number of moles of sodium?

  Use moles = mass / molar mass
• What is the molar mass of sodium?

  23 g/mol
• How many moles of sodium are in 115 grams?


  5 moles
• What is the mole ratio between sodium and sodium oxide in the reaction?

  2 moles of sodium produce 1 mole of sodium oxide
• How many moles of sodium oxide are produced from 5 moles of sodium?

  2.5 moles
• How do you find the mass of sodium oxide produced?

  Use mass = moles × molar mass
• What is the molar mass of sodium oxide (Na₂O)?

  62 g/mol
• What is the mass of 2.5 moles of sodium oxide?

  155 grams
• What are the steps to calculate the mass of a product from a limiting reactant?

  1. Identify the limiting reactant
  2. Write and balance the chemical equation
  3. Calculate moles of the limiting reactant
  4. Use mole ratios to find moles of product
  5. Calculate the mass of the product using its molar mass
• What is the significance of excess reactants in a chemical reaction?

  • They do not limit product formation
  • They remain after the reaction is complete
  • They can be reused in future reactions
• What are the products of the reaction between hydrochloric acid and calcium carbonate?

  • Calcium chloride
  • Water
  • Carbon dioxide