Question

We have an aqueous solution that contains 29% (by mass) of a hypothetical solute Z. The formula weight of the solute Z is 242 g/mol. The density of the solution is observed to be 1.5 g/mL. What is the molarity of Z in this solution? Answer in units of mol/L.

Answer 1

Answer:

The molarity of Z in this solution is 1.80 mol/L

Explanation:

29% (by mass) means that in 100 g of solution, you have 29 grams of solute.

So, by the solution density we can find our volume.

Density = mass / volume

Solution density = mass solution / volume solution

1.5 g/ml = 100 g / volume solution

volume solution = 100 g/ 1..5 g/ml

volume solution = 66.6 mL

So we have just found out that in 66.6 mL, we have 29 g of solute Z, so if we want to know the molarity, we have to find out the mass in 1 L, and afterwards, calculate the moles, we have

1000 mL = 1L

66.6 mL ____ 29 g of solute Z

1000 mL ____ (29 g . 1000 mL)/ 66.6 mL = 435.4 g

With the molar mass (formula weight), we can find out the moles

Mass /Molar mass = Mol

435.4 g /242 g/m = 1.80 mol

Molarity is 1.80 mol/L