How many grams of Na Cl molecular weight 58.5 g mole -1 would you dissolve in water to make a 50 mM Na Cl solution with 500 ml final volume?

By definition, a 50 mM solution of any substance contains 50 mM of the solute per liter of solution, and true solutions are always homogeneous mixtures. Therefore, 500 ml of such a solution would contain (50)(500/1000) or 2.50 millimoles of NaCl. The molecular weight of the salt Is stated in the question to be 58.5 grams per mole; therefore, the millimolecular mass would be 58.5 milligrams; and 2.50 times that value or 146 mg, to the justified number of significant digits , would be contained in 500 ml of the solution and would need to be supplied from the stock of NaCl available.