molekyylipainoska

Molekyylipainoska, Finnish term for a molecular weight scale, is a concept used in chemistry to describe a way of expressing and comparing the weights of molecules. It refers to a numerical convention that assigns a value to a molecule reflecting its relative molecular weight, typically expressed in daltons (Da) or in grams per mole (g/mol). In practice, the molecular weight in daltons of a compound equals its molar mass in g/mol, so the numbers on the scale are interchangeable across these two units.

The term is not an official SI unit but a pedagogical or descriptive expression common in Finnish educational contexts. It emphasizes that heavier molecules receive larger numbers, aiding qualitative comparisons of size and reactivity, especially in introductory chemistry.

Calculation and examples: molecular weight is obtained by summing the atomic weights of all atoms in the molecular formula. For example, water (H2O) has a molecular weight of about 18.015 g/mol (or 18.015 Da per molecule). Carbon dioxide (CO2) has about 44.01 g/mol (44.01 Da). For polymers, the scale becomes more approximate due to varying chain lengths and isotopic composition.

Limitations: the value depends on isotopic composition and the level of rounding; molecular weight is not a fixed property for mixtures or polymers without specifying the exact formulation. In practice, scientists often use precise molar masses for calculations and use the term “molecular weight” interchangeably with “molar mass.”

See also: molecular weight, molar mass, dalton, atomic weight.