Here it says to calculate the molarity of a solution prepared by dissolving two 3.7 grams of sodium hydroxide in enough water to make 2.50 liters of solution. So here we're looking for molarity. So molarity here equals our moles of solute, which would be the NaOH. And it is. And it's in a solution of 2.50 liters. So we need liters of solution.
All right, we already have the 2.50 liters of solution, so we just need to convert the grams of sodium hydroxide into moles. So one mole of sodium hydroxide goes on the bottom, and then grams of sodium hydroxide go. One mole goes on the top and grams of sodium hydroxide go on the bottom. Sodium hydroxide is composed of one sodium, one oxygen and one hydrogen. Multiply them by their atomic masses from the periodic table and then add up the totals. This will give us the molar mass of sodium hydroxide.
So when we add that all up, it's 39.998 grams. So that's going to go here. So here grams of sodium hydroxide cancel out and now I'm going to have moles of sodium hydroxide. So that comes out to 0.5925 moles. Take that and plug it in and we'll have the molarity of our solution. So this comes out to 0.237 molar for our solution.