The entropy unit is a non-S.I. unit of thermodynamic entropy, usually denoted "e.u." and equal to one
calorie per kelvin per mole, or 4.184
joules
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied. ...
per kelvin per mole.
Entropy units are primarily used in chemistry to describe
enthalpy
Enthalpy , a property of a thermodynamic system, is the sum of the system's internal energy and the product of its pressure and volume. It is a state function used in many measurements in chemical, biological, and physical systems at a constant ...
changes.
Sources
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Units of measurement