For the reactions shown below, we added 2.25 mL of 0.0500 M HCl to a test tube containing one of the two cations (Ag+ or Pb2+) and recovered 0.0161 g of precipitate.
AgNO3(aq) + HCl(aq) → AgCl(s) + HNO3(aq)
Pb(NO3)2(aq) + 2 HCl(aq) → PbCl2(s) + 2 HNO3(aq)
How much precipitate in moles would be recovered theoretically if the ion was Ag+?

Question

For the reactions shown below, we added 2.25 mL of 0.0500 M HCl to a test tube containing one of the two cations (Ag+ or Pb2+) and recovered 0.0161 g of precipitate.
AgNO3(aq) + HCl(aq) → AgCl(s) + HNO3(aq)
Pb(NO3)2(aq) + 2 HCl(aq) → PbCl2(s) + 2 HNO3(aq)
How much precipitate in moles would be recovered theoretically if the ion was Ag+?

aaronq · Answer

At first glance it seems that you'd need to know the concentration of silver nitrate solution, but knowing that the Ksp is really really small (and the fact that that information is omitted), we can assume that the concentration of AgCl in solution is negligible (in other words, it all precipitated).

So i think they're merely asking you to convert the mass recovered to moles.

$\sf moles=\dfrac{mass}{Molar~mass}$

cometailcane · Answer

So 0.0161 g / the molar mass of AgCl?

aaronq · Answer

yes divide the mass by the moar mass