This is the 3749th most frequent Russian word.
химических
"Chemical" (adjective form).
Here, "химических" is used as an adjectival form modifying "веществ," meaning "chemical substances." It pertains to the category or nature associated with chemicals.
На заводе производится широкий ассортимент химических веществ.
The factory produces a wide range of chemical substances.
In this sentence, "химических" describes "процессов," indicating processes that involve or are related to chemistry or chemicals.
Ученые изучают влияние химических процессов на окружающую среду.
Scientists study the influence of chemical processes on the environment.
The word "химических" acts as an adjective modifying "реакций," showcasing reactions related to chemical principles.