molecuulgewichtsverdeling

Molecuulgewicht, also known as molecular weight or relative molecular mass, is a measure used in chemistry to express the mass of a molecule. In modern terms, the mass per amount of substance is typically called molar mass, with units of grams per mole (g/mol). The relative molecular mass, a dimensionless quantity denoted Mr, is the ratio of the mass of a molecule to 1/12 the mass of a carbon-12 atom, and it numerically matches the molar mass when standard atomic weights are used.

To compute the molecular weight of a compound, the atomic weights of its constituent atoms are summed according to the chemical formula. For example, water (H2O) has a molecular weight of about 18.015 g/mol (2 × 1.008 for hydrogen plus 15.999 for oxygen). Glucose (C6H12O6) has a molecular weight of about 180.156 g/mol.

The term molecular weight is sometimes used interchangeably with molar mass, but technically molar mass has units and Mr is unitless. Isotopic composition can slightly alter the exact numeric value, since atomic weights are weighted averages of isotopes.

Molecular weight is used in stoichiometry, preparation of solutions, and quality control, to convert between mass and amount of substance. Measurements typically rely on calculated values from formulas or experimental techniques such as mass spectrometry, which can determine monoisotopic masses or average molar masses. The concept remains fundamental in chemistry and biochemistry for quantifying reactions and properties of substances.