Activity

high-resolution terminology - matching measurements at high-resolution

Activity

Description

The activity (relative activity) of a dissolved substance X equals the concentration, cX [mol/L] at high dilution (this applies frequently to dilutions <10 mmol/L) divided by the unit concentration, c° = 1 mol/L:

aX = cX/c°

For dissolved gases, the activity is the partial pressure, pX [Pa], devided by the unit partial pressure, p° = 1 Pa. The partial pressure is related to the concentration of the gas by the solubility, SX [Pa/mol]:

aX = cX*SX/p°

In general, the relative activity is defined by the chemical potential, µX '"`UNIQ--ref-00000001-QINU`"'

aX = exp[(µX-µ°)/RT]

The activity is a dimensionless quantity.

Abbreviation: a

Reference: Cohen 2008 IUPAC Green Book

MitoPedia concepts: Ergodynamics 

MitoPedia topics: Substrate and metabolite 

Activity in other contexts

• Activity of a radioactive substance, A = — dNB/dt [Bq]
• Catalytic activity
• Free ROUTINE activity, ROUTINE activity