Answer:
The entropy decreases.
Step-by-step explanation:
The change in entropy in a chemical reaction is lower when the moles of the gas product decrease. In the same way, the change in entropy is higher when the moles of the gas product increase.
For the reaction:
K(s) + O₂(g) ⟶ KO₂(s)
The number of moles of gas reactant is one (1 mole of K and 1 mole of O₂) and there are not moles of gas in product. The change in moles of gas is 1.
As the number of moles of product decrease the entropy decreses.
I hope it helps!