Obtain an expression for the entropy per particle, in terms of temperature and density,

Obtain an expression for the entropy per particle, in terms of temperature and density, for a classical ideal monatomic gas of N particles of spin S adsorbed on a surface of area A. Obtain the expected values of H, H², H³, where H is the Hamiltonian of the system. What are the expressions of the second and third moments of the Hamiltonian with respect to its average value?