What is the mole fraction?

Question

Calculate the mole fraction of MgI₂ in an aqueous solution prepared by dissolving 0.400 moles of MgI₂ in 850.0 g of water.

Answer 1

Mole fraction is moles of interest divided by total moles.

molar mass H₂O = 18.0 g/mol

moles MgI₂ present = 0.400 mols

moles H₂O = 850.0 g x 1 mol / 18 g = 47.2 mols

Total moles = 47.2 + 0.400 = 47.2 mols

mol fraction MgI₂ = 0.400 / 47.2 = 0.00847