Conservation of Mass

• What is the principle of conservation of mass in a chemical reaction?

  Mass is always conserved; no atoms are destroyed or created.
• What does it mean when we say that mass is conserved during a chemical reaction?

  It means the number and types of atoms are the same on both sides of the reaction equation.
• In the reaction 2Li + F₂ → 2LiF, how many lithium and fluorine atoms are present on each side of the equation?

  There are 2 lithium atoms and 2 fluorine atoms on each side.
• How can you demonstrate that mass is conserved using relative formula masses in the reaction 2Li + F₂ → 2LiF?

  By adding the relative formula masses of the reactants and products and comparing them.
• What is the total relative formula mass of the reactants in the reaction 2Li + F₂?

  51.8
• What is the total relative formula mass of the products in the reaction 2Li + F₂?

  51.8
• What happens to the mass in an unsealed reaction vessel if a gas is involved and the mass appears to increase?

  The mass increases because a gas from the air reacts and becomes part of the products inside the vessel.
• Why might the mass of an unsealed reaction vessel decrease during a reaction?

  The mass decreases because a gas product escapes from the vessel.
• In the example of a metal carbonate decomposing, what happens to the mass if the reaction vessel is not sealed?

  The mass appears to decrease as carbon dioxide gas escapes.
• What is the key takeaway regarding the conservation of mass in chemical reactions?

  • Total mass of reactants equals total mass of products.
  • No atoms are lost or gained during the reaction.
• How would you show that mass is conserved in the reaction H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O?

  By calculating and comparing the total mass of reactants and products.
• What is the balanced equation for the reaction involving sulfuric acid and sodium hydroxide?

  H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O