Question

Kc = [Na+][Cl-]/[NaCl(s)]
The above equation contains the concentration of NaCl in solid NaCl. This concentration is related to the density of solid NaCl
and its molar mass. Since the density of NaCl or of any pure solid or pure liquid does not vary with the extent of a reaction, the
concentration of any pure solid or liquid can be regarded as a constant and, thus, can be further absorbed into the equilibrium constant

density =mass/volume so density of solid or liquid does not channge, is this because the volume of the solid or liquid does not depends on the container it is in, it is the amount of substances its self?

Answer 1

yeah I think you are right, get a second opinion

Answer 2

I don't see that you have said anything wrong; however, the Kc you have written makes no sense to me. If NaCl actually exists as Na^+ and Cl^-, then what do you substitute into the equation for NaCl? zero? Well, equations can't be divided by zero. Thermodynamically, the concn of a solid (like NaCl) or a liquid (like water) are 1 (more technically, the activity is 1) for any material in its natural state at room T.