One way the US Enviro × Agency (EPA) tests for chloride contaminants in water is

Question

One way the US Enviro × 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 chioride precipitate. Suppose an EPA chemist tests a 200. ml sample of groundwater known to be contaminated with iron(!) chloride, which would react with silver nitrate solution like this: FeCl2(aq) 2 AgNO3(aq) 2 AgCl(s) + Fe(NO3)(aq) The chemist adds 57.0 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 2.4 mg of silver chloride. Calculate the concentration of iron(II) chloride contaminant in the original groundwater sample. Round your answer to 2 significant digits. x In

Explanation / Answer

mass of AgCl = 2.4 mg = 2.4*!0^-3 g

mol = mass/MW = (2.4*10^-3)/(143.32 ) = 0.000016745

then

mol of Ag = 0.00001674

ratio is 1:2

0.00001674 mol of Ag = 1/2*mol of FeCl2

mol of FeCl2 = 0.00001674*0.5

mol of FeCl2 = 0.00000837

mass = mol*MW = 0.00000837*126.751 = 0.0010609 g = 0.0010609*10^3 mg = 1.06 mg

V = 200 mL = 0.2

C = mass/V = 1.06 /0.2 = 5.3 mg /L

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.