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 merge 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 cadium chloride, which would react with silver nitrate solution like this:

CuCl2 (aq) + 2AgNO3 (aq) -> 2AgCl(s) + Cu(NO3)2 (aq)

The chemist adds 43.0mM silver nitrate solution to the sample until silver chloride stops forming. She then washes, dries, and weighs the precipitate. She finds she has collected 8.9mg of silver chloride.

Calculate the concentration of cadium chloride contaminant in the original groundwater sample. Round your answer to 2 important digits.