Gravimetric Analysis to calculate wgt%?

Antonio8

A solid 0.5330-g sample which contains only AgNO3(s) and Hg2(NO3)2(s) is dissolved in aqueous medium and the metal cations are precipitated as a mixture of the respective insoluble cobalticyanide salts.
3Ag+(aq) + Co(CN)63−(aq) → Ag3[Co(CN)6](s)
3Hg22+(aq) + 2Co(CN)63−(aq) → (Hg2)3[Co(CN)6]2(s)
The washed and dried precipitate has mass 0.5571 g.
What was the wt% of AgNO3 in the original sample?


I tried to solve this using (weight precipitate)*(gravimetric factor)(100) / weight of sample but i got the wrong answer!? can someone please shed some light on this for me !?

Borek

Which gravimetric factor? Your precipitate is a mixture of TWO solids.

The idea behind this type of the question is to write two independent equations - for example assume n_Ag (number of moles of Ag) and n_Hg2 are your unknowns. Express masses of the initial and final mixtures using these numbers of moles (and respective molar masses) and you have two equations in two unknowns - just solve.

But I have a feeling it won't work as expected in this case, as the system of equations is ill-conditioned (or perhaps they are even just dependent).