[blackflag10]

A 2.000-g sample of a solid mixture containing only PbCl2 (FM 278.1), CuCl2 (FM 134.45),
and KCl (FM 74.55) was dissolved in water to give 100.0 mL of solution.  First 50.00 mL of
the unknown solution was treated with sodium piperidine dithiocarbamate (NaX) to precipitate 
0.7268 g of lead piperidine dithiocarbamate (PbX2)   FW of PbX2 = 527.77

Then, 25.00 ML of unknown sol'n was treated with HIO3 to precipitate 0.8388 g of Pb(IO3)2 and Cu(IO3)2

FW of PB(IO3)2= 557

FW of Cu(IO3)2 = 413.35

Calculate the wt & of Cu in unknown mixture.

[Arkcon]

So, from the context of the question, the first reaction only affects lead, and you can use the formula weight to determine grams.  The second reaction allows you to determine the grams of copper and lead together.  The rest must be KCl, and the total must be 2.00 grams.  You're going to have to pull all that together to solve the problem.