Mole Calculations

• What is the first step to balance equations using reacting masses?

  Divide the mass of each substance by its Mr.
• Why is it necessary to divide the number of moles by the smallest number of moles in a reaction?

  To find the simplest whole number ratio of the reactants and products.
• If the moles of substances are not whole numbers, what should you do next?

  Multiply all the numbers by the same amount to make them whole numbers.
• What is the final step in balancing a chemical equation using reacting masses?

  Write the balanced symbol equation for the reaction using the whole numbers found.
• In the example provided, how many grams of metal X were burned in oxygen?

  25.4 g
• How do you calculate the number of moles of a substance?

  By dividing the mass of the substance by its molar mass (Mr).
• If you have 17 g of oxygen, how many moles does it represent given that the molar mass of oxygen is 16 g/mol?

  1. 06 mol
• What is the ratio of moles of X to moles of O₂ in the reaction example provided?

  1. 2.65
• What is the balanced equation for the reaction of metal X with oxygen?

  4X + 5O₂ → 20X oxide
• What is a limiting reactant in a chemical reaction?

  The reactant that is completely consumed first, limiting the amount of product formed.
• In the example with zinc oxide and carbon, how many grams of zinc oxide were used?

  81.4 g
• What is the balanced chemical equation for the reaction of zinc oxide with carbon?

  2ZnO + C → 2Zn + CO₂
• How do you determine the limiting reactant using moles?

  By comparing the mole ratio of the reactants to the ratio in the balanced equation.
• In the reaction of ZnO and C, which reactant was in excess?

  ZnO
• What is the limiting reactant in the reaction of 84 g of nitrogen gas with 12 g of hydrogen gas to produce ammonia?

  Hydrogen gas
• What are the steps to balance equations using reacting masses?

  1. Divide the mass of each substance by its Mr.
  2. Divide the number of moles of each substance by the smallest number of moles.
  3. If needed, multiply all the numbers by the same amount to make them whole numbers.
  4. Write the balanced symbol equation for the reaction.
• What is the process to find the limiting reactant in a chemical reaction?

  1. Calculate the moles of each reactant.
  2. Divide by the smallest number of moles.
  3. Compare the mole ratio to the balanced equation to identify the limiting reactant.
• What is the humorous phrase mentioned about moles in the study material?

  What do moles have for pudding? Jam moly-poly...
• What is the question posed at the end of the study material for practice?

  Q1: What is the limiting reactant when 84 g of nitrogen gas reacts with 12 g of hydrogen gas to produce ammonia?