molekulmasside

Molekulmasside are the masses of individual molecules. They are most commonly expressed in Daltons (Da) or as molar mass in units of kilograms per mole (kg/mol) or, more often in chemistry, grams per mole (g/mol). The two ways of expressing mass are related: 1 Da is numerically equal to 1 g/mol, so the molecular mass in Daltons roughly equals the molar mass in g/mol.

The molecular mass of a compound is obtained by summing the atomic masses of all atoms in its molecular formula. This sum can be based on standard atomic weights from the periodic table or on precise isotopic masses when exact isotopic composition is known. For many practical purposes the average atomic masses are used, yielding the relative molecular mass (often called molecular weight in older literature).

Molekulmasside can be measured or estimated for any molecule, from simple diatomic species to large organic or biomolecules. For example, water (H2O) has a molecular mass of about 18.015 Da, corresponding to a molar mass of approximately 18.015 g/mol. Glucose (C6H12O6) has a molecular mass near 180.156 Da and a molar mass around 180.156 g/mol. Complex macromolecules may have molecular masses that span thousands or millions of Da.

Applications involve stoichiometry, where molar masses convert between mass and amount of substance, and analytical techniques such as mass spectrometry, which directly measures molecular mass. It is important to distinguish between the exact molecular mass (per molecule) and the molar mass (per mole of molecules), as they are linked but used in different contexts.