For a system of NaCl(s) and NaCl(aq) in equilibrium, find the number of degrees of freedom (f) if the solid is considered to consist of the single species NaCl and the solute species present in solution:
a. is considered to be NaCl(aq);
b. are taken to be Na+(aq) and Cl-(aq).
c. Must your answers for (a) and (b) be the same? Why or why not?