Mass of calcium = 240g
Molar mass of calcium = 40g
Number of moles in 40g of calcium = 1 mole
Therefore, number of moles in 240g of calcium = 240 / 40 = 6 moles
Mass of magnesium = 240g
Molar mass of magnesium = 24g
Number of moles in 24g of magnesium = 1 mole
Therefore, number of moles in 240g of magnesium = 240 / 24 = 10 moles
Therefore, mole ratio of 240g of calcium to 240g of magnesium is 3:5.