molekylvægten

Molekylvægten, also known as molecular weight, is a fundamental concept in chemistry. It represents the sum of the atomic weights of all atoms in a molecule. Atomic weights are typically expressed in atomic mass units (amu). To calculate the molecular weight of a compound, one needs to know its chemical formula and the atomic weights of each element present in that formula. For example, to determine the molecular weight of water (H₂O), you would add the atomic weight of oxygen (approximately 16.00 amu) to the atomic weights of two hydrogen atoms (each approximately 1.01 amu), resulting in a molecular weight of approximately 18.02 amu.

Molecular weight is a crucial property for various chemical calculations and applications. It is used in stoichiometry to determine the amount of reactants and products in a chemical reaction. It also plays a role in understanding the physical properties of substances, such as boiling point and melting point, as larger molecules generally have higher molecular weights and therefore stronger intermolecular forces. Furthermore, molecular weight is essential for determining molar mass, which is the mass of one mole of a substance and is numerically equivalent to the molecular weight but expressed in grams per mole (g/mol). This distinction between molecular weight (in amu) and molar mass (in g/mol) is important in practical laboratory work.