3.5 Limiting Reactants

• What is the main topic of today's video?

  The main topic is limiting reactants and their effect on calculations.
• What happens when hydrochloric acid reacts with calcium carbonate?

  They produce calcium chloride, water, and carbon dioxide.
• How can we observe that a reaction is taking place between hydrochloric acid and calcium carbonate?

  The solid calcium carbonate will slowly disappear and bubbles of gas will be given off.
• What indicates that one of the reactants has been completely used up in the reaction?

  The reaction stops and the fizzing slows down and eventually stops.
• What do we call the reactant that limits the amount of product that can be produced?

  The limiting reactant.
• What is the status of hydrochloric acid when calcium carbonate is the limiting reactant?

  Hydrochloric acid is in excess.
• What happens if more calcium carbonate is added to the reaction?

  More fizzing will occur as more products are made until the calcium carbonate is used up again.
• What happens if more hydrochloric acid is added to the reaction?

  Nothing will happen because there is no calcium carbonate to react with.
• What is combustion in the context of sodium burning in air?

  Combustion means reacting with oxygen.
• In the example of burning sodium, which reactant is assumed to be in excess?

  Oxygen is assumed to be in excess.
• What is the first step in calculating the mass of sodium oxide produced?

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

  Use the equation moles = mass / mr.
• What is the molar mass (mr) of sodium?

  The molar mass of sodium is 23 g/mol.
• How many moles of sodium are in 115 grams?

  There are 5 moles of sodium.
• What is the ratio of sodium to sodium oxide in the balanced equation?

  The ratio is 2:1.
• How many moles of sodium oxide are produced from 5 moles of sodium?

  1. 5 moles of sodium oxide are produced.
• How do you calculate the mass of sodium oxide produced?

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

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

  The mass is 155 grams.
• What is the significance of the limiting reactant in a chemical reaction?

  • It determines the maximum amount of product that can be formed.
  • Once it is consumed, the reaction stops.
  • The amount of excess reactant does not affect the amount of product.
• What are the steps to calculate the mass of a product formed in a reaction?

  1. Write and balance the chemical equation.
  2. Calculate the number of moles of the limiting reactant.
  3. Use the mole ratio to find moles of the product.
  4. Calculate the mass of the product using mass = moles × mr.