The Mole and Equations

• What do the numbers in front of chemical formulas represent in a balanced equation?

  They indicate the number of moles
• In the reaction MgO + 2HCl → MgCl2 + H2, how many moles of hydrochloric acid are used?

  2 moles
• What can you determine if you know the masses of reactants and products in a reaction?

  You can find the balanced symbol equation
• What are the steps to balance equations using reacting masses?

  1. Divide mass by relative formula mass
  2. Divide moles by smallest number of moles
  3. Multiply to get whole numbers if needed
  4. Write the balanced symbol equation
• How do you calculate the relative formula mass of zinc oxide (ZnO)?

  By adding atomic masses: 65 + 16
• What is the relative formula mass of carbon dioxide (CO₂)?

  44
• How many moles of zinc oxide (ZnO) are produced from 8.1 g?

  0.10 mol
• How many moles of carbon (C) are in 0.60 g?

  0.050 mol
• What is the balanced symbol equation for the reaction of zinc oxide and carbon?

  2ZnO + C → CO₂ + 2Zn
• What is the relative atomic mass of nitrogen (N)?

  28
• What is the relative atomic mass of hydrogen (H)?

  2
• What is the relative atomic mass of ammonia (NH₃)?

  17
• What is the significance of practicing calculations in chemistry?

  • Helps understand balancing equations
  • Reinforces mole calculations
  • Builds confidence in quantitative chemistry