posted by julie jung .
Given 4K + O2 → 2K2O, what is the reaction type?
Did you replace anything? So it can't be 1 or 2.
Did you decompose anything? That is, did you take something and make smaller somethings? No
So it must be synthesis. Synthesis occurs when smaller somethings combine to make bigger somethings.
By the way I think K and O2 combine to make K2O2, potassium peroxide.