CBSE Class 9 Answered

Molar mass, symbol M, is the mass of one mole of a substance (chemical element or chemical compound).^[2] It is a physical property which is characteristic of each pure substance. The base SI unit for mass is the kilogram but, for both practical and historical reasons, molar masses are almost always quoted in grams per mole (g/mol or g mol^–1), especially in chemistry.

Molar mass is closely related to the formula weight (F.W.) or relative molar mass (M_r) of a compound, and to the relative atomic masses or the standard atomic weights of its constituent elements. However, it should be distinguished from the molecular mass , which is the mass of one molecule (of any single isotopic composition) and is not directly related to the atomic mass, the mass of one atom (of any single isotope). The dalton, symbol Da, is also sometimes used as a unit of molar mass, especially in biochemistry, with the definition 1 Da = 1 g/mol, despite the fact that it is strictly a unit of molecular mass (1 Da = 1.660 538 782(83)×10^–27 kg).