A variety of ions including #Na^+#, #K^+#, #NH_4^+#, #Pb^(2+)#, #Fe^(2+)#, #NO_3^-#, #Cl^-#, #Br^-#, #S^(2-)#, and #CO_3^(2-)# are mixed in a beaker of water. If you analyzed the precipitates which substances would you expect to find?

1 Answer
anor277
Jun 22, 2017

Well, you would expect to find FIRST of all, sulfide salts of the transition and main group metal ions.......

Explanation:

Precipitates......#FeS(s)#, #PbS(s)#, #PbCl_2(s)#, #PbBr_2(s)#.....

Possibly some #PbCO_3(s)#, but there might be proton transfer to form #HCO_3^(-)# ions.........(and bicarbonate salts tend to be soluble).

How do we know these sulfides and halides are insoluble? How else but by experiment? Note that the solubilities of these salts are extensively tabulated.

There is are general rules for assessing solubilities in aqueous solution:

All the salts of the alkali metals and ammonium are soluble.

All nitrates, and perchlorates are soluble.

All halides are soluble EXCEPT for # AgX, Hg_2X_2, PbX_2"#.

All sulfates are soluble EXCEPT for #PbSO_4, BaSO_4, HgSO_4#.

All carbonates and hydroxides are insoluble. All sulfides are insoluble.

The given rules follow a hierarchy. Alkali metal and ammonium salts tend to be soluble in all circumstances. The one exception to this rule is #K^(+)BPh_4# and #NH_4^(+)BPh_4#, both of which are as soluble as bricks. #Na^(+)""^(-)BPh_4# is sold as #"kalignost"#

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