Dalton (unit)

Last revised by Daniel J Bell on 29 Jan 2021

The dalton (symbol: Da), also known as an atomic mass unit, is a unit of mass that is equal to one twelfth of the mass of a free carbon-12 atom at rest. Its value is approximately equal to 1.660 x 10−27 kg. The molar mass of an entity, when measured in daltons, is approximately equal to the sum of the protons and neutrons in the entity. For example, the 45 atoms in a molecule of sucrose C12H22O11 have 182 protons and 160 neutrons between them, giving a total of 342 particles. The molar mass of sugar is 342.299 daltons.

The molar weight of large molecules can be expressed in kilodaltons or megadaltons as appropriate.

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