Calculating Masses

• What happens to reactions when one reactant is used up?

  Reactions stop when one reactant is used up
• What does the amount of product formed in a reaction depend on?

  The amount of product depends on the limiting reactant
• If 105 g of aluminium is burned in air, what is being calculated?

  The mass of aluminium oxide formed
• What is the mass of magnesium needed to make 100 g of magnesium oxide?

  The mass of magnesium needed is calculated based on the reaction
• What is the chemical equation for the reaction between chlorine and potassium bromide?

  Cl₂ + 2KBr → 2KCl + Br₂
• How do you calculate the mass of bromine produced from 23.8 g of potassium bromide reacting with excess chlorine?

  By using stoichiometry based on the balanced equation
• What is the concept of a limiting reactant in chemical reactions?

  • The limiting reactant is the substance that is completely consumed in a reaction.
  • It determines the maximum amount of product that can be formed.
  • Once it is used up, the reaction stops.
• What steps are involved in calculating the mass of a product formed in a chemical reaction?

  1. Write the balanced chemical equation.
  2. Identify the limiting reactant.
  3. Use stoichiometry to relate reactants to products.
  4. Calculate the mass of the desired product.