Calculating Masses in Reactions

Question 1

What are the 3 important steps of Calculating Masses in Reactions?

Answer 1

1) Write out the balanced equation
2) Work out Mᵣ - just for the 2 bits you want
3) Apply the rule: Divide to get one, then multiply to get all

Question 2

Worked example: What mass of magnesium oxide is produced when 60g of magnesium is burned in air?

Answer 2

1) Balanced equation = 2Mg + O₂ -> 2MgO
2) Mᵣ (only the bits you need) = 2*24 -> 2(24+16)
= 48 -> 80
3) Divide to get one, then multiply to get all
48g of Mg………80g of MgO
1g of Mg………….1.67g of MgO
60g of Mg………100g of MgO
Answer = 100 g