Final answer:
Molar mass provides the link between the mass of a substance in grams and the number of moles of that substance, allowing calculations that connect mass with the microscopic number of atoms or molecules.
Step-by-step explanation:
Molar mass provides a relationship between the number of moles of a substance and the number of grams of the same substance. The molar mass (M) is the mass of one mole of a substance and is measured in grams per mole or g.mol⁻¹. The numerical value of an element's molar mass is equivalent to its relative atomic mass or, for molecules and ionic compounds, its molecular or formula mass.
The formula that defines the relationship between moles (n), mass in grams (m), and molar mass (M) is n = m / M. This allows us to calculate the number of moles in a given mass of a substance, or conversely, to find the mass if we have the number of moles. For example, to compute the number of moles from a known mass of a substance, we divide the mass by the substance's molar mass, which serves as the conversion factor.
To calculate the number of atoms or molecules in a sample, we use Avogadro's number, which is the number of units in one mole (approximately 6.022×10²³ entities). The mole is a fundamental unit in chemistry for quantifying the amount of substance, connecting the macroscopic scale of mass with the microscopic scale of atoms or molecules.