For cations copper,aluminium,lead,zinc,iron,ammonia,calcium and magnesium. Write the reagent for confirming and observations
Answers
Answer:
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Explanation:
Confirmatory tests should be performed on separate solutions of some of your ions, in order to see what these tests look like before using them on an unknown. Generally a confirmatory test is used only after other reactions have been used to isolate the ion. When working with stock solutions of an ion, dilute 1 drop with 9 drops of water to simulate the concentration that would exist in an unknown. In a mixture or a solution obtained from an unknown or known mixture, the dilution is not necessary since the ions have already been diluted compared to the stock solutions. In the tests described here, it is assumed that 10 drops of solution will be used. If you change the amount of solution of the ion being tested, you must also adjust the amounts of the reagents to be added.
Tests Based on Hydrogen Sulfide
Antimony, Sb3+
Cadmium, Cd2+
Mercury(II), Hg2+
Tests Based on Other Reagents
Aluminum, Al3+
Ammonium, NH4+
Bismuth, Bi3+
Calcium, Ca2+
Chromium, Cr3+
Cobalt, Co2+
Copper, Cu2+
Iron, Fe3+
Magnesium, Mg2+
Manganese, Mn2+
Mercury(I), Hg22+
Mercury(II), Hg2+
Nickel, Ni2+
Silver, Ag+
Strontium, Sr2+
Tin, Sn2+
Zinc, Zn2+
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A. Tests Based on Hydrogen Sulfide
Even if hydrogen sulfide was not used for separation of ions, it may be useful for confirmatory tests.
The most convenient and safe source of H2S is thioacetamide. When heated, aqueous solutions of thioacetamide hydrolyze to produce H2S:
In acid solution:
CH3CSNH2 + 2H2O + H+ --> CH3COOH + NH4+ + H2S
In basic solution using ammonia:
CH3CSNH2 + 2H2O + 2NH3 --> CH3COO- + 3NH4+ + S2-
In basic solution using strong base:
CH3CSNH2 + 2OH- --> CH3COO- + NH3 + S2- + H2O
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Antimony, Sb3+
To 10 drops of solution, add 6 M NH3(aq) until neutral. Make the solution acidic by adding one or more drops of 6 M HCl. Add 1 mL of thioacetamide and stir well. Heat the test tube in the boiling water bath for 5 minutes. If antimony is present, a red orange precipitate of antimony sulfide should form. This same test will also work with arsenic(III),
tin(II),
and tin(IV).
These precipitates are yellow, brown, and yellow, respectively.
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Cadmium, Cd2+
Three related procedures can be used.
a. Follow the procedure described for antimony(III). The precipitate should be yellow.
b. Follow the procedure described for antimony(III), but first make the solution basic with aqueous ammonia. If a precipitate forms on addition of ammonia, continue to add ammonia until the precipitate dissolves, before adding the thioacetamide.
c. Add ammonia, as described in procedure b. Then add 10 drops of water and 10 drops of 6 M NaOH. A white precipitate should form. If it does not form, either increase the amount of NaOH, or do not add the 10 drops of water. Centrifuge and discard the solution. Wash the precipitate twice with a mixture of 1 mL of water and 1 mL of 6 M NH3(aq). Dissolve the precipitate by adding 6 M HCl drop by drop until no precipitate remains. Add 6 M NaOH until the solution is just basic. A white precipitate of Cd(OH)2 will form. Then add 1 mL of 1 M thioacetamide and heat the mixture in a boiling water bath for 5 minutes. A yellow precipitate of CdS will form.
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Mercury(II), Hg2+
Follow the procedure described for antimony(III). The precipitate should be black.
Try to dissolve the precipitate in 1 mL of 12 M HCl with heating. If it does not dissolve in HCl, try the same procedure with 1 mL of 6 M (dilute) HNO3. If it still does not dissolve, then try to dissolve it in a mixture of 1 mL of 6 M HCl and 1 mL of 6 M HNO3, heating for 2 minutes in a water bath. Most of the black precipitate should dissolve. Mercury(II) sulfide is the least soluble of the metal sulfides.