Consider the following generic equilibrium in which a solid reactant is in equilibrium with a gaseous product. A(s) == B (g). The following diagrams represent the reaction mixture at the following points: (a) initially; (b) after a short period of time has passed; and (c) at equilibrium. For each diagram, calculate the concentrations of the spheres representing A(s) and B(g). Assume that each block in the grid has an area of 1 cm^2 and report your answer in units of (Since the spheres in the solid are not free to move, the solid only occupies the area that it covers. The spheres in the gas, however, are free to move and therefore occupy the entire grid.) What do you notice about the concentrations of A(s) and B(g) in these representations? Write an equilibrium expression for the generic reaction and use the results of your calculations to explain why A(s) is not included in the expression.