Question

The density of a solution of magnesium sulfate (MW = 120.4) with 2.16 molality at the freezing point of water is about 1.25 g/mL. What is the molarity of this solution?

Answer 1

Answer:

2.70M

Explanation:

Molality is an unit of concentration defined as the ratio between moles of solute and kg of solution. Molarity is defined as the ratio between moles of solute and liters of solution. That means to solve this question it is necessary to convert kg to liters of solution.

Assuming 1kg in the solution, moles of solution are 2.16 and liters are:

1kg × (1000g / 1kg) × (1mL / 1.25g) × (1L / 1000mL)  = 0.80L

Thus, molarity is:

2.16moles / 0.80L = 2.70M

I hope it helps!