Conservation of mass

• Chemical equation


  Reaction information shown using word and symbol equations
• Mass is conserved in chemical reactions
• No atoms are made or destroyed in chemical reactions
• Relative atomic mass


  Used to find the relative formula mass of a compound
• The total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning
• This is because no atoms are created or destroyed during chemical reactions
• The principle of conservation of mass allows you to work out the mass of one substance in a reaction if the masses of the other substances are known
• Calcium carbonate


  • 28 grams of calcium oxide + 22 grams of carbon dioxide = 50 grams of calcium carbonate
• Magnesium oxide


  • 48 grams of magnesium + unknown amount of oxygen = 80 grams of magnesium oxide
• In practice, it is not always possible to get the entire calculated amount of product from a reaction
• Reasons why the entire calculated amount of product may not be obtained


  • Reversible reactions may not be completed
  • Some product may be lost when removed from the reaction mixture
  • Some of the reactants may react in an unexpected way