Answer :
AgI should precipitate first.
The concentration of when CuI just begins to precipitate is,
Percent of remains is, 0.0076 %
Explanation :
for CuI is
for AgI is
As we know that these two salts would both dissociate in the same way. So, we can say that as the Ksp value of AgI has a smaller than CuI then AgI should precipitate first.
Now we have to calculate the concentration of iodide ion.
The solubility equilibrium reaction will be:
The expression for solubility constant for this reaction will be,
Now we have to calculate the concentration of silver ion.
The solubility equilibrium reaction will be:
The expression for solubility constant for this reaction will be,
Now we have to calculate the percent of remains in solution at this point.
Percent of remains =
Percent of remains = 0.0076 %