Input the mass of solute and the volume of the resulting solution to calculate the molarity (M, in moles/liter) of several common water-soluble salts. The number of moles equals the mass divided by the molecular weight MW. Generally, since the volume of the solution is only very slightly changed by addition of solute, it is usually a sufficiently accurate approximation to compute molarity as moles of solute divided by volume of solvent.
In highly accurate work, an alternative measure of concentration, molality, can be used. The molality is given by moles of solute per kg of solvent and so does not depend on the variation of solution volume with temperature or with addition of solute. In this case, the solvent volume in mL is reinterpreted as solvent mass in g.