Themes > Science > Chemistry > General Chemistry > Solution and Solubility > Solubility of Solutes and Aqueous Solutions > Solution Index > Molarity The molarity of a solute is the number of moles of that solute divided by the volume of the solvent in liters. It's the handiest measure for most aqueous solutions, since we are usually interested in the number of moles of the solute, but we work with volumes. To figure out the molarity of a solution, simply work out the number of moles of the solute (Probably from the molecular weight) and divide by the volume of the solvent molarity (M) = moles solute/liters of solutionTo convert a volume and a molarity of a solution to moles of solute, simply solve the above equation for moles of solute: moles solute = molarity * liters of solution Example 1: If you have 10.0 grams of NaCl, table salt, and dissolve it in 500 ml of water, what is the molarity of the solution? Solution 1: First, work out the number of moles of salt. NaCl has a molecular weight of 58.43 g/mole, so we have 10.0 g/58.43 g/mole = 0.171 moles of NaClNext, convert the volume to liters, since it is in milliliters 500 ml * 1 liter/1000 ml = 0.500 literNow simply use the equation above molarity (M) = moles solute/liters of solution M = 0.171 moles/0.500 L = 0.342 M Example 2: How many moles of Ba(NO3)2 are there in 250 ml of a 0.450 M solution? Solution 2: Again, we need to convert milliliters to liters, so 250 ml * 1 L /1000 ml = 0.250 LNow just use the equation above to solve for the number of moles moles solute = molarity * liters of solution moles Ba(NO3)2 = 0.450 mol/L * 0.250 L = 0.113 moles Information provided by: http://learn.chem.vt.edu