Pre-exponential factor

{
  "id": "MLC-T-CHM-009377",
  "term": "Pre-exponential factor",
  "field": "Chemistry",
  "definition": "The constant 'A' in the Arrhenius equation, k = A exp(-Ea/RT), which represents the frequency of collisions between reactant molecules with the correct orientation for a reaction to occur. It is also known as the frequency factor. This factor has the same units as the rate constant, k, and can vary significantly depending on the reaction.",
  "synonyms": [
    "Arrhenius A factor",
    "A-factor"
  ],
  "subject": "Physical and Biophysical Chemistry",
  "see_also": [
    "coefficient",
    "activation"
  ],
  "references": [
    "Green Book, 2nd ed., p. 56 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)",
    "PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 177 (https://doi.org/10.1351/pac199668010149)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/pre-exponential-factor/"
}