5.23 - Calculations using reacting masses

Question 1

What can we use to work out how much of a product will be formed in a reaction?

Answer 1

• The balanced equation of the reaction

- The mass of the reactant

Question 2

What is the 4 step process for calculating the amount of product formed in a reaction?

Answer 2

• Calculate all molar masses you can
• Calculate the number of moles of the reactant
• Use the ratio to calculate the number of moles of the product
• Calculate the mass of the product

Question 3

What mass of sulfur trioxide is needed to form 75.0g of sulfuric acid?

Answer 3

• Mr of SO3 = 80.1
  Mr of H2SO4 = 98.1
• Moles of sulfuric acid = 75/98.1 = 0.765 moles
• Ratio = 1:1, so moles of SO3 = 0.765
• Mass of sulfur trioxide = 0.765 * 80.1 = 61.2g

Question 4

What is a hydrate?

Answer 4

A compound containing water of crystallisation

e.g. CuSO4.5H20