Using scanning tunneling microscopy (STM) and molecular beam techniques, we have studied the SiCl spatial distribution after annealing Cl-covered Si(111)-7x7 surfaces with different initial spatial correlations between adsorbed SiCl. At room temperature, the spatial correlation between adsorbed SiCl is a function of Cl-2 incident energy. At an incident energy of 0.11 eV, SiCl island formation as well as isolated-site adsorption are observed. However, at an incident energy of 0.44 eV, no island formation occurs and only isolated-site adsorption is observed. The isolated-site adsorption results in SiCl singles with no neighboring SiCl as well as paired SiCl. Annealing all of these Cl-covered surfaces to similar to 600 degrees C for 60 s results in similar surface morphology even though the spatial correlations between adsorbed SiCl on these surfaces before annealing are different. The annealing process results in the complete destruction of SiCl islands and pairs and an increase in the density of adatom vacancies as well as SiCl singles on the surface. One new adatom vacancy is created for each two SiCl species desorbed. The change in surface site can be explained by the recombinative desorption process, SiCl(s) + SiCl(s) --> Si(s) + SiCl2(g), in which diffusion of SiCl plays an important role. The second-order desorption of SiCl2 can be envisioned as a slow 2D lattice-gas reaction of SiCl species on the Si(111)-7x7 surface at high temperature.