Calculate the molality of a 15.0% by mass solution of MgCl₂ in H₂O. The density of this solution is 1.127 g/mL. A)0.157 m B)11.8 m C)1.86 m D)0.0134 m E)1.58 m

Question

Quizplus · Accepted Answer

To calculate the molality of the solution, we need to first convert the percentage by mass to grams of MgCl2 per 100 grams of solution.

15.0% by mass means that there are 15.0 g of MgCl2 in 100 g of solution.

Next, we need to calculate the moles of MgCl2 in 1000 g (1 L) of solution using its molar mass:
Molar mass of MgCl2 = 24.305 g/mol + 2(35.453 g/mol) = 95.21 g/mol

Moles of MgCl2 in 1000 g (1 L) of solution = 15.0 g / 95.21 g/mol = 0.1574 mol

Finally, we can calculate the molality of the solution by dividing the moles of solute by the mass in kg of the solvent.
Mass of solvent = 1000 g - 150.0 g = 850.0 g = 0.8500 kg

Molality = 0.1574 mol / 0.8500 kg = 1.86 m

Therefore, the correct answer is (C) 1.86 m.

Calculate the Molality of a 15