Write the expression for the equilibrium constant Keq for the reaction below:

2KClO3(s) ⇔ 2KCl(s) + 3O2(g)

A [KClO3] / [KCl] [O2]
B [KClO3]^2 / [KCl]^2 [O2]^3
C [KCl] [O2] / [KClO3]
D [KCl]^2 [O2]^3 / [KClO3]^2

Keq = [O2]³

Explanation:

Step 1: Data given

For the reaction aA + bB ⇄ cC + dD

The Keq is [C]^c * [D]^d  / [A]^a * [B]^b

Step 2: The balanced equation

2KClO3(s) ⇔ 2KCl(s) + 3O2(g)

For 2 moles KClO3 we have 2 moles KCl and 3 moles O2

Step 3: Calculate Keq for this reaction

For the reaction aA ⇄ cC + dD

The Keq is [C]^c * [D]^d  / [A]^a

Pure solids and liquids are not included in the equilibrium constant expression. This is because they do not affect the reactant amount at equilibrium in the reaction, so they are disregarded and kept at 1. Remember that the activity, a, of any solid or liquid in a reaction is equal to 1

The correct answer here is: Keq = [O2]³

But since it is not an option i would opt for option D, which is the closest to correct.

Keq =  [KCl]² *[O2]³ / [KClO3]²

but technically it's not correct. If there is an option 'none of the above' it would be better.