using molarity to find solute mass and solute volume

Question

Calculate the volume in liters of a 0.0023 mM calcium sulfate solution that contains 125.g of calcium sulfate CaSO4. Round your answer to 2 significant digits.

Answer 1

Monica,

In your comment, you said you got 399.205 but you didn't include units. Also, the correct number of sig. figs. should be 2 so your answer would round to 4.0x10²

Here is my solution to the problem:

molar mass CaSO₄ = 136 g/mol

0.0023 mM = 0.0023 mmol / L

125 g CaSO₄ x 1 mol / 136 g = 0.919 mols CaSO₄ = 919 mmols CaSO₄

919 mmol / x L = 0.0023 mmol / 1 L

x = 399,565 L = 4.0x10⁵ L

(Please be sure to check my math)