This is the 9601st most frequent Russian word.
химическая
"Chemical."
In this sentence, 'химическая' describes the word 'формула', indicating it's related to chemistry (a chemical formula).
Химическая формула воды - H2O.
The chemical formula of water is H2O.
Here, 'химическое' modifies 'оборудование', implying the equipment is used in or related to chemical processes.
На заводе установили новое химическое оборудование.
A new chemical equipment was installed at the factory.
In this example, 'химическую' refers to 'реакцию', signifying the reaction pertains to chemistry (a chemical reaction).