Molar mass is the mass of one mole of a substance, typically measured in grams per mole (g/mol). It represents the total mass of all the atoms in a molecule, calculated by adding the atomic masses of each element present in the compound. For example, the molar mass of water H2O is approximately 18 g/mol, derived from two hydrogen atoms and one oxygen atom. Molar mass is essential in chemistry for converting between the mass of a substance and the number of moles. This conversion is crucial for stoichiometry, which involves calculating the amounts of reactants and products in chemical reactions. Understanding molar mass helps chemists accurately measure and mix substances in experiments.