Question

STOREOMETRY Solving for a reactant in solution 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 tin(II) chloride, which would react with silver nitrate solution like this: SuCl(aq) + 2 AgNO3(aq) + 2 AgCl(s) + Su(NO) (mm) The chemist adds 70.0 mM silver nitrate solution to the sample until silver chloride stops forming. He then washes, dries, and weighs the precipitate. He finds he has collected Some of silver chloride Calculate the concentration of intl) chonde contaminant in the original groundwater sample. Be sure your answer has the correct number of significant digits.

Answer 1

Molar mass of silver chloride = 143.5 g

Molar mass of SnCl2 = 189.6 g

287 g AgCl needed = 189.6 g SnCl2

8.0 mg AgCl needed = 189.6×8.0/287 => 5.3 mg

Concentration = 5.3/0.250 => 21. mg/L

So concentration of SnCl2 = 21. mg/L