Final answer:
The task calculates solute species concentration in solutions with a common ion, applying the common ion effect and using solubility or equilibrium constants, taking into account whether the contribution of ions from the solute's dissolution is negligible.
Step-by-step explanation:
The task involves calculating the concentration of solute species in solutions containing a common ion without considering water ionization. The basis for these calculations is that the presence of a common ion will suppress the dissolution of the solute due to the common ion effect. This is similar to utilizing the concepts in calculating the ionization of weak acids or bases. We will use the respective solubility product constants (Ksp) or relevant equilibrium constants for solubility predictions.
As for the examples given, such as TlCl in HCl, PbI2 in CaI2, Ag2CrO4 in a K2CrO4 solution, or Cd(OH)2 in a buffered solution, the principle is that the high concentration of the common ion in the solution will make the additional contribution to the ion concentration from the solute's dissolution negligible. This is termed the common ion effect, and it significantly impacts solubility.
When considering whether to neglect changes in initial concentrations of common ions, this is appropriate when the change is minuscule compared to the initial concentration. For example, in a solution with a high concentration of HCl, the additional Cl- ions from TlCl's dissolution will barely alter the concentration of Cl- in solution. Conversely, in a solution with a much lower concentration of a common ion, changes might not be negligible, and thus equilibria need to be examined closely through equilibrium expression and stoichiometry to find the final concentrations.