standard reaction quantities

https://doi.org/10.1351/goldbook.S05923
Infinitesimal changes in thermodynamic functions with
extent of reaction
divided by the infinitesimal increase in the extent when all the reactants and products are in their standard states. For the quantity X they should be denoted by ΔrX, but usually only ΔX is used. For specific types of reactions the subscript r is replaced by: f for formation, c for combustion, a for atomization and superscript ‡ for
activation
.
Source:
Green Book, 2nd ed., p. 52 [Terms] [Book]