Are you certain that your answer is incorrect? Ksp=[Pb][CrO4], and as you add K2CrO4, you are increasing the concentration of CrO4 in solution, and the equilibrium position must shift such that the amount of Pb and CrO4 decreases. This is accomplished by precipitating PbCrO4. It will continue to shift as you add more, and the fact that K2CrO4 is in excess implies that it is added until things stop changing; this occurs when essentially all of the Pb in solution has been precipitated. Thus, there should have been .0022mol Pb ions in solution, making for a concentration of .022M of Pb2+ and .044M Cl-. But of course I could very well be wrong. I would be very interested in knowing, given that I take my chemistry AP test on Tuesday.