Cu++ forms a blue-green complex with tetraphenylporphin in a 1:1 ratio. Say you have 100 mL of a 2.0 x 10^-4 solution of the Tetraphenylporphin. Exactly what weight of CuCl2 must be added to the solution to insure complete complexation without any excess cupric chloride remaining?

How many mols of the tetraphenylporphin do you have? That's mols = M x L = ?

Since the ratio is 1:1 you have that same number of mols Cu^2+ and the same number of mols of CuCl2.

Then mass CuCl2 = mols CuCl2 x molar mass CuCl2.