Question

Verify by calculating that

1. 5 moles of CO₂ and 5 moles of H₂O do not have the same mass.
2. 240 g of calcium and 240 g magnesium elements have a mole ratio of 3 : 5.

Answer 1

(a) Mass of one CO₂ = 44g
Mass of 5 moles of CO2 
= 44 × 5 
= 220g
Mass of one mole of H₂O = 18

Mass of 5 moles of H₂O 

= 18 × 5 

= 90g

(b) Molar mass of Ca = 40g = 1 moles

Number of moles in 240g of Ca = `240/40` = 6

Molar mass of Mg = 24g = 1 mole

Number of moles in 240g of Mg = `240/24`

= 10

Mole ratio of Ca and Mg = 6 : 10 or 3 : 5