One way the U. S. Environmental Protection Agency (EPA) tests for chloride contaminants in water is by titrating a sample of silver nitrate solution. Any chloride anions in solution will combine with the silver cations to produce bright white silver chloride precipitate. Suppose an EPA chemist tests a 250 mL sample of groundwater known to be contaminated with nickel(II) chloride, which would react with silver nitrate solution like this: NiCl2 (aq) + 2AgNO3 (aq) -> 2AgCl (s) + Ni(NO3)2 (aq) The chemist adds 74.0 mM silver nitrate solution to the sample until silver chloride stops forming. She then washes, dries, and weighs the precipitate. She finds she has collected 8.3 of silver chloride. Calculate the concentration of nickel(II) chloride contaminant in the original groundwater sample. Show your work!

Explanation:

One way the U.S. Environmental Protection Agency (EPA) tests for chloride contaminants in water is by titrating a sample of silver nitrate solution. Any chloride anions in solution will combine with the silver cations to produce bright white silver chloride precipitate. Suppose an EPA chemist tests a 200.mL sample of groundwater known to be contaminated with copper(II) chloride, which would react with silver nitrate solution like this: CuCl2 (aq) + 2AgNO3 (aq) ? 2AgCl (s) + CuNO32 (aq) The chemist adds 26.0m M silver nitrate solution to the sample until silver chloride stops forming. She then washes, dries, and weighs the precipitate. She finds she has collected 6.1mg of silver chloride. Calculate the concentration of copper(II) chloride contaminant in the original groundwater sample. Be sure your answer has the correct number of significant digits.