Final answer:
The equilibrium constant expression for the reaction P4O10(s) ⇌ P4(s) + 5 O2(g) is given by Kp = (PO2)^5, considering only the gaseous species involved in the equilibrium.
Step-by-step explanation:
To express the equilibrium constant for the given reaction P4O10(s) ⇌ P4(s) + 5 O2(g), we need to write an expression in terms of the partial pressures of the products and reactants, following the general format of Kp = (products)coefficients / (reactants)coefficients. In this case, solids do not appear in the equilibrium expression as they have a constant concentration. Therefore, we get: Kp = (PO2)5 for the reaction.
Since P4O10 and P4 are both in the solid state, they are not included in the expression for Kp. The only gas present is oxygen (O2), so its partial pressure raised to the fifth power is used for the expression of the equilibrium constant in terms of partial pressures (Kp).