Using precipitation and selective dissolution develop a flow chart (procedure) f
ID: 996899 • Letter: U
Question
Using precipitation and selective dissolution develop a flow chart (procedure) for separating a sample containing all six cations using the reactions studied and a centrifuge. Note, you should begin with all six ions in one solution and have each ion as the only ion in a solution or as the cation in a precipitate.
Reaction
Ag+
Ba2+
Cr3+
Cu2+
Fe3+
Zn2+
1) Precipitation with chloride ion
2) Precipitation with sulfate ion
3) Precipitation of hydroxide with NH3
4) Precipitation of hydroxide with NaOH
5) Precipitation with phosphate ion
5a) Dissolution of insoluble phosphate salt in strong acid
5b) Dissolution of insoluble phosphate salt in NaOH
5c) Dissolution of insoluble phosphate salt in NH3
Reaction
Ag+
Ba2+
Cr3+
Cu2+
Fe3+
Zn2+
1) Precipitation with chloride ion
2) Precipitation with sulfate ion
3) Precipitation of hydroxide with NH3
4) Precipitation of hydroxide with NaOH
5) Precipitation with phosphate ion
5a) Dissolution of insoluble phosphate salt in strong acid
5b) Dissolution of insoluble phosphate salt in NaOH
5c) Dissolution of insoluble phosphate salt in NH3
Explanation / Answer
1. When we add Cl- ion via HCl, all the chlorides will be soluble except Ag+ which will form insoluble AgCl and thus can be centrifuged and separated out, leaving the rest of the metal ions in solution
2. Then we add H2SO4, so that the metal ions forms sulfates, all the sulfates are soluble except BaSO4, and that can be centrifuged and thus Ba2+ separated.
3. Then we add aq. NH3 till the solution becomes basic. Cu2+, which forms insoluble precipitate Cu(OH)2 as blue ppt., which can be centrifuged and separated.
4. Then when we add NaOH to the remaining solution, F3+ form insoluble Fe(OH)3 and thus can be centrifuged and separated
5. (a) when we add H3PO4, both Cr3+ and Zn2+ forms insoluble phosphate salts CrPO4 and Zn3(PO4)2. but when we add strong acid, CrPO4 becomes soluble in acidic solution and thus can be separated.
(b)the left precipitate is that of zinc and thus separated
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