Concentrations of solutions in chemistry are usually expressed as molarity, which is the number of moles of solute per liter of solution. To find the molarity of a solution requires knowing the mass of dissolved solute the volume of the solution and molar mass of the solute. Molarity is defined as the number of moles of solute dissolved in 1 liter of solution.. Molarity Formula is given below. Thus molarity has the units moles per liter (mol L-1).