Question

An aqueous NaCl solution is made using 113 g of NaCl diluted to a total solution volume of 1.25 L .

A.) Calculate the molarity of the solution.

B.) Calculate the molality of the solution. (Assume a density of 1.08 g/mL for the solution.)

C.) Calculate the mass percent of the solution. (Assume a density of 1.08 g/mL for the solution.)

Answer 1

A)

Mass of NaCl = 113 g

Molar Mass of NaCl = 58.5 g / mol

=> Moles of NaCl = 113 / 58.5 = 1.932 moles

Molarity = Moles of NaCl / Volume of Solution (L)

=> Molarity = 1.932 / 1.25 = 1.55 M

B)

Molality = Moles of solute / Mass of Solvent (in Kg)

Density of solution = 1.08 g / mL

=> Mass of solution = 1.25 x 1000 x 1.08 = 1350 g

Mass of solvent = 1350 - 113 = 1237 g = 1.237 kg

=> Molality = 1.932 / 1.237 = 1.56 m

C) Mass % = Mass of NaCl x 100 / Mass of solution

=> Mass % = 113 x 100 / 1350 = 8.37 %