Final answer:
The equilibrium constant for the reaction P4(s) + 5 O2(g) ⇌ P4O10(s) is expressed as K = (1) / ([O2]^5), where [O2] is the partial pressure of the oxygen gas.
Step-by-step explanation:
To express the equilibrium constant for the reaction P4(s) + 5 O2(g) ⇌ P4O10(s), we can use the general expression for the equilibrium constant K in terms of the concentrations or partial pressures of the reactants and products. However, in this reaction, since both the reactants and products that are solids (P4 and P4O10) do not appear in the expression for K as their concentrations are constants, the equilibrium constant expression simplifies considerably. The expression for K will only involve the gaseous reactants, which in this case is oxygen (O2). The expression for K will be:
K = (1) / ([O2]5)
Note that we include the exponent 5 because the balanced reaction involves 5 moles of O2 gas. Since P4 and P4O10 are in the solid phase, they do not appear in the expression for K. The equilibrium constant expression does not include the concentrations of any pure solids or liquids.