Question

O CHEMICAL REACTIONS 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 Iron(III) chloride, which would react with silver nitrate solution like this: FeCl3(aq) + 3 AgNO3(aq) - 3 AgCl(s) + Fe(NO3),(aq) The chemist adds 86.0 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 2.5 mg of silver chloride. Calculate the concentration of Iron(III) chloride contaminant in the original groundwater sample. Round your answer to 2 significant digits. X 5 ?

Answer 1

Chemical equ?: - Fellz (aq) + 3 AgNO₃(aq) 3 Agcl (8) + Fe(NO3)₂ (aq) Molar mass - 16d. 29/mol 143,32g/mol The precipitates formed are of Agci, silver chloride. . Mass af Agei fermed = 2.5 mg = 0.0025g (19=1000 mg | The chemical equi. shows that 3 moles of Agcl is formed from I mole of feelze This means; (3x 143.32 g/mol) 3 moles of Agel formed by = 162.2 g of fellz (1 mole? then 0.0025g of Agcl must be formed from; 162.2 2a Feliz x 0,0025g Agte 0.000943 g fells Thus 429.968 Agch amount of fella contaminated in 250ml water = 0.943 mg. concentration of fella in mg/l = 0.943mg 0.850 = 3.772 mg/l on rounding to 2 sig. figures = [ 3.8 mg/L) 215 216