उत्तर : 2. "पदार्थ के एक मोल के ग्राम में व्यक्त द्रव्यमान"
व्याख्या :

In chemistry, the molar mass of a chemical compound is equal to the ratio of the mass of a sample of that compound and the amount (in moles) of the substance present in that sample. Its SI unit is kilogram/mol. But gram/mol is its practical unit.