One way the U.S. Environmental Protection anions in solution will combine with t

Question

One way the U.S. Environmental Protection anions in solution will combine with the silver cations to produce bright white sliver chloride precipitate Agency (EPA) tests for chloride contaminants in water is by titrating a sample of silver nitrate solution. Any chioride Suppose an EPA chemist tests a 250. ml. sample solution like this: of groundwater known to be contaminated with coppertt) chioride, which would react with siver nitrete CuCl (aa)+2 AgNO,(ag) 2AgcIs) Cu(NO,) o) be contaminated with The chemist adds 53.0 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 7.3 mg of silver chloride. Calculate the concentration of copper(I) chloride contaminant in the original groundwater sample. Round your answer to 2 significant digits 100 O Type here to search

Explanation / Answer

molar mass of AgCl= 143.5 g/mole

moles of AgCl collected = mass/molar mass= 7.3*10-3 gm/143.5 =5.1*10-5 moles

moles of CuCl2 to be used from the the reaction is CuCl2+ 2AgNO3------->2AgCl(s)+ Cu(NO3)2(aq) is

moles of silver nitrate= 53*10-3*0.25 =0.01325. This is the excess reactant since theoretical ratio of CuCl2: AgNO3= 1:2 where as actual ratio iis 5.1*10-5 :0.01325

5.1*10-5 moles . mass of CuCl2= molar mass* moles of CuCl2=134.5 g/mole = 5.1*10-5*134.5 =0.0068 gm = 6.8 mg

But volume of sample collected= 250 ml = 250/1000L=0.25L, concentration of CuCl2= 6.8mg/0.25L= 27.2 mg/L

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