Answer to Question #299830 in General Chemistry for แพรว

Question

What is the mole fraction of the solute that contains 10.0 grams of Phosphorus pentachloride that has been dissolved in 750 mL of water?

Answer 1

Solution:

solute = phosphorus pentachlorid = PCl₅

solvent = water = H₂O

The molar mass of PCl₅ is 208.24 g/mol

Hence,

Moles of PCl₅ = (10.0 g PCl₅) × (1 mol PCl₅ / 208.24 g PCl₅) = 0.048 mol PCl₅

The density of water is around approximately 1 g cm⁻³

Hence,

Mass of H₂O = (750 mL H₂O) × (1 g H₂O / 1 cm³ H₂O) × (1 cm³ H₂O/ 1 mL H₂O) = 750 g H₂O

The molar mass of H₂O is 18.015 g/mol

Hence,

Moles of H₂O = (750 g H₂O) × (1 mol H₂O / 18.015 g H₂O) = 41.632 mol

Mole fraction (χ) of PCl₅ = Moles of PCl₅ / Total moles of solution

Total moles of solution = Moles of PCl₅ + Moles of H₂O = 0.048 mol + 41.632 mol = 41.680 mol

Hence,

Mole fraction (χ) of PCl₅ = 0.048 mol / 41.680 mol = 0.00115

Mole fraction (χ) of PCl₅ = 0.00115

Answer: The mole fraction of the solute (PCl₅) is 0.00115