A 1M (1 molar) sodium hydroxide (NaOH) solution is prepared by dissolving approximately 40 grams of NaOH in enough water to make a final volume of 1 liter. This requires weighing the NaOH quickly due to its hygroscopic nature, dissolving it in water, and then adding water up to the 1-liter mark in a volumetric flask. The molarity can also be determined by standardizing it against a primary standard, such as potassium hydrogen phthalate.