General Chemistry: Molar Mass from Molarity & Density

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MCAT practice question: A well-sealed flask found in a laboratory is said to contain a 3 M solution of an unidentified compound. The solution is measured to be 2.5 L and to have a density of 2 g/mL. The molar mass of this compound is closest to:

A. 15 g/mol

B. 67 g/mol

C. 150 g/mol

D. 667 g/mol

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I have the answer, but my book does not have a very good explanation and further confused me. I understand that two important equations for this problem include density = mass/volume and molarity = mol solute/volume of solution. Where I am most confused is how these two are related enough to get molar mass of the compound.

Thank you for your time!

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EDIT: g/mol –> g/mL

In: Chemistry