How do you solve this?

Question

Calculate the volume in liters of a 0.00747 mol/L calcium sulfate solution that contains 150.g of calcium sulfate CaSO4.Round your answer to 3 significant digits.

Answer 1

HI Marco,

0.00747 mol/L means that there are 0.00747 moles of CaSO₄ in 1L of solution.

Since we're trying to find the volume and we don't have moles to directly work with, the best thing to do first is to convert the 150. g of CaSO₄ to moles.

We can do this by dividing by the molar mass of CaSO₄

Molar mass of CaSO₄ = 136.14 g/mol

This means that 1 mole of CaSO₄ = 136.14 g of CaSO₄

Using this relationship, we can calculate the no. of moles in 150.g by dividing by the molar mass

150. g x 1 mol/136.14 g = 1.10 moles

Using the previous relationship that 0.00747 moles of CaSO₄ in 1L of solution, we can calculate the volume that has 1.10 mols of CaSO₄

We divide by the molarity ---------- 1.10 mols CaSO₄ x 1L/0.00747 mols CaSO₄ = 147 L

Answer 2

How many moles CaSO₄ are in 150. g?

molar mass CaSO₄ = 136 g/mol

150. g CaSO₄ x 1 mol / 136 g = 1.10 mols CaSO₄

How many liters of 0.00747 mol/L CaSO₄ contains 1.10 mols?

1.10 mols x 1 L / 0.00747 mols = 147.26 L = 147 L (3 sig. figs.)