Question

A 20.3 mass % aqueous solution of iron(III) chloride has a density of 1.280 g/mL. Calculate the molality of the solution. Give your answer to 2 decimal places.

Answer 1

Answer:

Molality for the solution is 1.57 m

Explanation:

Molality is mol of solute in 1kg of solvent.

20.3 % by mass means that 20.3 g of solute (FeCl₃) are contained in 100 g of solution..

Let's determine the mass of solvent.

Mass of solution = Mass of solvent + Mass of solute

100 g = Mass of solvent + 20.3 g

100 g - 20.3 g = Mass of solvent → 79.7 g

Let's convert the mass in g to kg

79.7 g . 1kg / 1000 g = 0.0797 kg

Let's determine the moles of solute (mass / molar mass)

20.3 g / 162.2 g/mol = 0.125 mol

Molality = 0.125 mol / 0.0797 kg → 1.57 m