Question

How could you prepare pure hydrated zinc chloride solid, Zn(H2O)6Cl2, (which is water soluble) and pure silver chloride from a solution containing only the Ag(H2O)2+, Zn(H2O)6 2+, and NO3- ions?

Answer 1

We can assume that solution contains Zinc nitrate and Silver nitrate.

1) Silver chloride formation is easy. We just need to add excess NaCl or excess HCl and white AgCl will precipitate.

AgCl is more stable as compared to other silver compounds that’s why it will only be formed.

Ag(H2O)2+ + Cl- à AgCl(↓)

Then we will be centrifuging the mixture and dry the precipitate to get solid AgCl.

Now the solution contains Zn(H2O)6 2+,NO3- and Cl-.

2) Zinc nitrate is soluble and quite in water. Therefore, it will be little difficult to precipitate zinc chloride directly without any reagent. But we have easiest way.

We can thermally decompose the Zinc nitrate to ZnO and then add HCl.

2 Zn(NO3)2 → 2 ZnO + 4 NO2 + O2

ZnO + 2HCl à ZnCl2(↓) + H2O