Dissociative surface reaction and its reverse, associative surface reaction, are defined by: \[2^{\text{*}}+\text{C}_{2}\text{H}_{5}^{\text{*}}\rightleftharpoons \text{H}^{\text{*}}+\,^{\text{*}}{\text{CH}_{2}\text{CH}_{2}}^{\text{*}}\] where * represents a surface site.
Source:
PAC, 1976, 46, 71. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units - Appendix II. Definitions, Terminology and Symbols in Colloid and Surface Chemistry. Part II: Heterogeneous Catalysis' on page 84 (https://doi.org/10.1351/pac197646010071)