Question

A solution contains the ions Ag , Pb2 , and Ni2 . Dilute solutions of NaCl, Na2SO4, and Na2S are available to separate the positive ions from each other. In order to effect separation, the solutions should be added in which order?

Answer 1

The solutions should be added in this order NaCl > Na2SO4 > Na2S

Step-by-step explanation:

Silver is insoluble as a chloride, so the silver ions get precipitated on addition of chloride ion as silver chloride. This means Ag+ would be removed the first.

So we will add NaCl in the first step.

The following reaction will occur.

Ag+ + Cl- → AgCl(s)

Both, Pb2 and Ni are soluble as chlorides. (lead chloride is soluble as a hot solution but will ppt when colder).

When we add Na2SO4, Pb2+ will get precipitated (because it's insoluble) as PbSO4 and Ni will remain soluble as NiSO4 is soluble in water.

The reaction that will occur is:

Pb^2+ + SO4^2- → PbSO4(s)

Nickel is insoluble as a sulfide. So when we will add Na2S, nickel will be precipitated as sulfide and be able to separate and be collected.

The solutions should be added in this order NaCl > Na2SO4 > Na2S