The molecular weight of NaOH, or sodium hydroxide, is 39.9971 g/mol. This means that one mole of this substance containing a number of constituent particles equal to Avogadro's constant, weighs 39.9971 grams.
Sodium hydroxide is a white solid ionic substance. It is soluble in polar solvents such as water or ethanol and insoluble in non-polar solvents such as ether. It is considered a strong chemical base and it reacts with acids to form sodium salts and water. It is a highly corrosive substance and thus it causes chemical burns when it touches the skin and permanent blindness when coming in contact with the eyes.