The concentration of the solid phase the quantity present. depends on changes with the amount of is equal to always remains the same regardless of

The concentration of the solid phase always remains the same regardless of the quantity present. Most of the chemical reactions and separation systems involve the transport of more or one components in solid phase.
For example, in the process of solid catalyzed reactions, the result of solid phase transport might be negligible though it is hard to identify it in the rate of data in the analysis.