Question

Answer QUESTION 5

Describe what happens at the molecular level once equilibrium is reached--that is, once the solution is saturated with Cu(IO_3)_2. Why must some solid remain in contact with a solution of a sparingly soluble salt in order to ensure equilibrium? Describe how you are going to calculate the [Cu^2+] for the saturated solution of copper iodate once you know the absorbance value of the copper ion. How will you use this concentration to find the K_sp value for copper iodate?

Answer 1

Equilibrium means the forward change and backward change should happen spontaneously. Now in case of sparingly soluble salt, lets say AgCl in water the forward reaction is AgCl(solid) = Ag+(solution) + Cl-(solution)

which is solid AgCl salt getting soluble in solution(here water) sparingly as Ag+ and Cl- ions. To be in equilibrium the reverse process should also happen i.e Ag+(solution) + Cl-(solution) = AgCl(solid)

That means the Ag+ and Cl- ions converts to the solid salt again.

Though the number of molecules are very less as it is sparingly soluble, but it has to exist otherwise the forward and backward reaction will be hampered and equilibrium condition wont exist anymore.