An aqueous solution containing 12.0% MgCl₂ by mass.What is the mol fraction of water in this solution? A)0.975 B)0.880 C)0.868 D)0.133 E)0.952

Question

Quizplus · Accepted Answer

The mol fraction of water in the solution can be calculated by first determining the mass of MgCl2 in 100 g of the solution (which is 12.0 g) and then calculating the mass of water (which is 88.0 g, since 100 g - 12 g = 88 g). Next, we convert the mass of MgCl2 and water to moles. The molar mass of MgCl2 is approximately 95.21 g/mol (24.31 g/mol for Mg + 2*(35.45 g/mol for Cl)). Thus, the moles of MgCl2 are 12.0 g / 95.21 g/mol ≈ 0.126 mol. The molar mass of water is 18.015 g/mol, so the moles of water are 88.0 g / 18.015 g/mol ≈ 4.886 mol. The total moles in the solution are 0.126 mol + 4.886 mol ≈ 5.012 mol. The mole fraction of water is then the moles of water divided by the total moles, which is 4.886 mol / 5.012 mol ≈ 0.975.

An Aqueous Solution Containing 12