Question

A chemist obtains 250.0 mL of a solution containing an unknown concentration of calcium iodide, CaI2. He pipets 25 mL of this solution into a 100 mL volumetric flask and dilutes to the mark. He then pipets 10 mL of this diluted solution into a 100 mL volumetric flask and dilutes to the mark. He analyzes some of the solution from the final volumetric flask and finds that the iodide ion concentration is 2.46E-6 (2.46 × 10-6) M. (Note: in solution, calcium iodide breaks apart into one Ca2+ ion for every two I- ions, so a solution that is 1.0 M in CaI2 is 2.0 M in I-.) Determine the molar concentration of calcium iodide in the original solution. Report your answer to the correct number of sig figs. Recall the precsion of volumetric pipets and flasks.