[en] Oxygen chemisorption heats are determined on supported V₂O₅/MgO and V₂O₅/Al₂O₃ catalyst containing from 1 to 15% wt. V₂O₅ at 25 deg C. It is shown, that during oxygen adsorption on V₂O₅/MgO formed is O₂^- with 20 kcal/mol adsorption heat and O^- with adsorption heat about 60 kcal/mol, which oxidize CO at 25 deg C. The total quantity of chemisorbed oxygen goes through the maximum with increasing V₂O₅ content. Oxygen adsorption heats on the V₂O₅/Al₂O₃ type catalysts exceed 60 kcal/mol for all the V₂O₅ concentrations; O₂^- ions are not formed on these catalysts. The total number of of adsorbed oxygen increases with increasing V₂O₅ concentration