Conservation of Mass

• What does it mean when we say no atoms are created or destroyed in a chemical reaction?

  Only the bonds between atoms change
• In the reaction of sodium and chlorine, how many sodium chlorides are formed?

  Two sodium chlorides are formed
• How do you balance a chemical equation using the conservation of mass principle?

  You ensure equal numbers of each atom on both sides
• What is the total relative formula mass of sodium and chlorine in the reaction?

  117
• How do you calculate the total relative formula mass on the left side of the sodium and chlorine reaction?

  2 times 23 for sodium plus 2 times 35.5 for chlorine
• If you react 2.3 grams of sodium with 3.5 grams of chlorine, what is the mass of sodium chloride produced?

  5.8 grams of sodium chloride
• Why might the mass appear to change during a reaction involving a gas?

  Gas can escape and not be measured
• What happens when magnesium reacts with oxygen?

  It forms magnesium oxide
• Why does magnesium oxide weigh more than magnesium?

  It includes the mass of oxygen from the air
• How much magnesium would produce approximately how much magnesium oxide?

  1 gram of magnesium produces about 1.6 grams
• What is the effect of conducting a reaction in a sealed container?

  It measures all reactants including gases
• What happens to the mass when calcium carbonate decomposes?

  It appears to decrease due to gas loss
• How does a sealed container affect the mass of products in a reaction?

  Mass remains constant as all gases are trapped
• What are the key points of the conservation of mass principle?

  • Mass is conserved in chemical reactions
  • No atoms are created or destroyed
  • Mass may appear to change with gases
  • Use sealed containers to measure accurately