A molar solution is one that contains one mole of solute per litre. A 1 molar solution is a solution in which 1 mole of a substance is dissolved in a total volume of 1 litre. For example the molecular weight of sodium chloride (NaCl) is 58.44, so one gram molecular weight (= 1 mole) of NaCl i.e. 58.44g, in a final volume of 1 litre = a 1M NaCl solution.