Solubility question.?

Question

I know the answer to this question is .25ml but do not know how to find the solution.

How many mL of a 0.001 M chloride solution must be added to a 100 mL solution of 7.2 × 10^−5 M Ag+ solution for AgCl to precipitate? Ksp (AgCl) = 1.8 × 10^−10 (Neglect dilution by the added Cl− solution.)

Answer 1

Ksp = [Ag+][Cl-]

you're given [Ag+] and Ksp so [Cl-] has to be equal to

2.6x10^-6 M to form a ppt.

so how much chloride solution need to be added to achieve this? Yes you've got the answer.