Solute concentration in a solution can be expressed in many ways. Molarity is the most commonly used unit to express concentration of a solute in a solution.
Molarity is defined as concentration of a solute in moles per liter.
For example, 1 M NaOH solution contains 1 mole in a liter of solution. 1 mole of NaOH is equal to 40 g of NaOH. In other words, 1 M NaOH solution contains 40 g of NaOH in a liter of solution. So to prepare 1M NaOH solution, 40 g of NaOH is dissolved in water to a final volume of 1 Liter.
Molar mass (= molecular weight) of solute: g/mole
Amount of the solute: g
Volume of the solution: ml