Reacting Masses

• What is the concept of moles used for in chemistry?

  To calculate the masses of reactants and products in chemical reactions.
• What is the relationship between moles and chemical equations?

  • Moles represent the amount of substance.
  • Coefficients in equations indicate the ratio of moles.
  • Moles can be used to calculate masses of reactants and products.
• How many moles of magnesium chloride are produced from one mole of magnesium and one mole of chlorine?

  One mole of magnesium chloride.
• How do you calculate the number of moles from mass and relative formula mass?

  By dividing the mass by the relative formula mass.
• What does a coefficient of two in front of hydrochloric acid indicate in a chemical equation?

  It means two moles of hydrochloric acid are needed.
• If you have 146 g of hydrochloric acid, how do you find the number of moles?

  By calculating 146 g / 36.5 g/mol.
• What is the relative formula mass of hydrochloric acid?

  36.5 g/mol.
• How do you determine the mass of magnesium chloride produced from hydrochloric acid?

  1. Calculate moles of hydrochloric acid.
  2. Use the mole ratio from the equation.
  3. Calculate moles of magnesium chloride produced.
  4. Multiply by the relative formula mass of magnesium chloride.
• What is the relative formula mass of magnesium chloride?

  95 g/mol.
• How do you calculate the mass of sodium sulfate from sodium hydroxide?

  By following the steps of calculating moles and using the mole ratio.
• What is the relative formula mass of sodium hydroxide?

  40 g/mol.
• If you have 240 g of sodium hydroxide, how many moles do you have?

  6 moles of sodium hydroxide.
• How many moles of sodium sulfate are produced from sodium hydroxide?

  3 moles of sodium sulfate.
• What is the relative formula mass of sodium sulfate?

  142 g/mol.
• What is the equation to calculate the number of moles of a chemical?

  Number of moles = mass of a chemical / relative atomic mass
• How do you calculate the mass of sodium sulfate produced from sodium hydroxide?

  By calculating 3 moles × 142 g/mol.
• How do you calculate the number of moles for compounds?

  Number of moles = mass / relative formula mass
• What is the final mass of sodium sulfate produced from 240 g of sodium hydroxide?

  426 g.
• Why is it important to know how to calculate relative formula mass before using the moles concept?

  Because it is necessary for calculating moles of compounds
• How do you calculate the mass of hydrogen peroxide needed to produce 64 g of oxygen?

  By following the steps of calculating moles and using the mole ratio.
• What is the relative formula mass of oxygen?

  32 g/mol.
• What is the process to calculate the mass of a product formed in a chemical reaction?

  • Identify the reactants and products in the chemical equation
  • Calculate the number of moles of the reactant
  • Use the mole ratio from the equation to find moles of the product
  • Calculate the mass of the product using its relative formula mass
• How many moles of oxygen are produced from 64 g?

  2 moles of oxygen.
• What does it mean if there are no large numbers in front of the chemicals in a chemical equation?

  It means that the ratio of moles is 1:1
• How many moles of hydrogen peroxide are needed to produce 2 moles of oxygen?

  Four moles of hydrogen peroxide.
• What is the relative formula mass of hydrogen peroxide?

  34 g/mol.
• How many moles of magnesium are produced from 72 g of magnesium?

  3 moles
• What is the final mass of hydrogen peroxide needed to produce 64 g of oxygen?

  136 g.
• How many moles of magnesium chloride can be produced from 3 moles of magnesium?


  3 moles
• What is the mass of magnesium chloride produced from 3 moles?

  285 g
• What steps would you take to calculate the mass of calcium sulfate produced from 80 g of calcium?

  • Calculate the number of moles of calcium: 80 g / 40 g/mol = 2 moles
  • Use the mole ratio: 2 moles of calcium produce 2 moles of calcium sulfate
  • Calculate the mass of calcium sulfate: 2 moles × 136 g/mol = 272 g
• How many moles of calcium oxide are produced from 224 g of calcium oxide?

  4 moles
• How many moles of calcium carbonate are needed to produce 4 moles of calcium oxide?

  4 moles
• What is the mass of calcium carbonate needed to produce 224 g of calcium oxide?

  400 g
• What is the importance of practicing calculations of reacting masses in chemistry?

  • Enhances understanding of stoichiometry
  • Prepares for solving real-world chemical problems
  • Builds confidence in using chemical equations