Calculations Based on Balanced Equations

• Calculations from Equations


  1. Balance the reaction

  2. Identify the mole ratio

  3. Calculate the no. of moles of one of the substances

  4. Use mole ratios from the equation

  5. Calculate the moles of the second substance using the mole ratio
• Mole ratio


  The quantities of the substances needed, like the quantities of ingredients needed to bake a cake
• The balanced chemical equation is like the recipe for baking a cake and the mole ratio is the quantities of the substances needed
• Balanced chemical equation


  N₂ + 3H₂ → 2NH₃
• Balanced chemical equation


  • Mole of N₂ can react to produce 2 moles of NH₃
  • 3 moles of H₂ are also needed to produce 2 moles of NH₃
• Calculation using a balanced chemical equation

  1. Balance the reaction

  2. Identify the mole ratio

  3. Calculate the no. of moles of one of the substances

  4. Use mole ratios from the equation

  5. Calculate the moles of the second substance using the mole ratio

  6. Convert from mole to mass using your triangles
• Combustion


  • What mass of carbon dioxide will be formed from 4g of methane (CH₄)?
• Reaction with excess hydrochloric acid

  • What mass of sodium chloride, NaCl is produced when 10.6g of sodium carbonate, Na₂CO₃, is reacted with excess hydrochloric acid?