A chemist observed that it would not readily dissolve in HCl, Solid black CuS is exceedingly insoluble, but would react with concentrated HNO3 resulting in a solution containing Cu2+, among other things. The chemist also observed the formation of a red-brown gas as the reaction proceeded. The chemist in question was a keen observer, but careless. When performing the reaction, he forgot to write down the mass of the CuS that he used. Being a conscientious chemist in all aspects of your work, you have offered to solve the problem for the careless chemist. The solution prepared by the chemist was transferred quantitatively into a 250mL volumetric flask and diluted to the mark after which a 20.0 mL aliquot was treated with excess KI. The resulting solution needed 77.33 mL of a 0.00812 M Na2S2O3 solution to reach equivalence. Explain what mass of CuS did the sloppy chemist use?