What is the molarity of a solution made by dissolving 5 grams of sodium chloride, in enough water to make 25 millilitres of solution? So a couple of things that I need to recall, before I get this problem started is one the definition of molarity. So molarity, capital M, equals moles of solute per liter of solution, and I also notice that I have 5 grams of NaCl, and I know that any time I'm dealing with these calculations I'm going to have to get it into moles, and so I'm going to need the molar mass. So the molar mass of sodium chloride, is the mass of sodium which is 23.0, plus chlorine, which is 35.5, and I'm going to find that I get a molar mass. Of 58.5 grams per mole for the sodium chloride. Now, I know that I'm going to need both mols and liters. I'm not going to try to do that all in one calculation. I'm going to focus first on finding the numerator, finding the mols of solute, and then I'll worry about getting the volume in the denominator. So, I know I'm given 5 grams of my sodium chloride. And I can use the molar mass of 58.5 grams per mol. G in there, 58.5 grams per mol to find the mols of sodium chloride. So, my grams are going to cancel with grams, I'm left with mols, and when I solve that, I get 0.0855 mols of NaCl or sodium chloride. Now look back to the problem, and look for that volume. And it gives me the volume in milliliters that can easily convert that to liters. So now when I'm ready to find the molarity, I can say 0.0855 mols of NaCl. And 0.250 liters of solution. And my molarity will be equal to 0.34 molar.