Conservation of Mass

• What is one of the most important concepts in chemistry?

  Conservation of mass
• What does the conservation of mass state in a chemical reaction?

  Mass is always conserved; no atoms are created or destroyed
• In the reaction of sodium and chlorine, how many sodium chlorides are formed?

  Two sodium chlorides
• Why do we need two sodiums on the left side of the sodium plus chlorine reaction?

  To balance the two chlorine atoms in the molecule
• How do we verify the conservation of mass using relative formula masses?

  By comparing total masses on both sides of the equation
• What is the total relative formula mass of sodium and chlorine in the reaction?

  117
• If 2.3 grams of sodium reacts with 3.5 grams of chlorine, what is the mass of sodium chloride produced?

  5.8 grams
• What happens to the mass during a reaction if a gas is involved?

  The mass might seem to change due to gas escaping
• What is the effect of heating magnesium in air?

  It forms magnesium oxide, which weighs more
• Why does magnesium oxide weigh more than magnesium alone?

  Because it includes oxygen from the air
• How does conducting an experiment in a sealed container affect mass measurement?

  It ensures all gases are accounted for
• What happens when calcium carbonate decomposes?

  It produces calcium oxide and carbon dioxide
• What occurs to the mass of products if carbon dioxide escapes during decomposition?

  The mass appears to decrease
• How does sealing a container affect the conservation of mass during a reaction?

  It prevents gas loss, maintaining mass balance
• What are the key points of the conservation of mass principle?

  • Mass is conserved in chemical reactions
  • Mass may appear to change with gases
  • Use sealed containers to maintain mass balance