1. Identify the reagent (and its concentration) that is used to confirm the presence of each of the following: a. Ni²+ b. Fe³+ c. Zn²+

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1. Identify the reagent (and its concentration) that is used to confirm the presence of each of the following:
a. Ni²+
b. Fe³+
c. Zn²+
2. Confirmatory tests for the various ions are often colorful. Identify the confirmatory compound/ion and the color for
each of the following ions:
Ion
Fe³+
Ni²+
A1³+
Zn²+
Confirmatory Compound/Ion
3. Identify the reagent that separates
a. Fe³+ from Zn²+. Explain the chemistry of the separation.
b. Fe³+ from Ni²+. Explain the chemistry of the separation.
c. Al³+ from Zn²+. Explain the chemistry of the separation.
Color
Transcribed Image Text:1. Identify the reagent (and its concentration) that is used to confirm the presence of each of the following: a. Ni²+ b. Fe³+ c. Zn²+ 2. Confirmatory tests for the various ions are often colorful. Identify the confirmatory compound/ion and the color for each of the following ions: Ion Fe³+ Ni²+ A1³+ Zn²+ Confirmatory Compound/Ion 3. Identify the reagent that separates a. Fe³+ from Zn²+. Explain the chemistry of the separation. b. Fe³+ from Ni²+. Explain the chemistry of the separation. c. Al³+ from Zn²+. Explain the chemistry of the separation. Color
A. Separation of
Ni²+ and Fe³+
from Zn²+ and Al³+
B. Test for
Iron(III) Ion
17b
13b
11
11f
C. Test for Nickel Ion
E. Test for 17b
Zinc Ion
13b
D. Test for Aluminum Ion
17b
The Next Step
11f
To digest the precipitate: to make the
precipitate more compact
11f
The Experimental Procedure is written for a single reference solution. If you are simul-
taneously identifying cations in both a reference solution and a test solution, adjust the
procedure accordingly. If the test solution is a sample with an environmental origin,
then gravity filter 10-15 mL before beginning the Experimental Procedure.
Prepare the hot water bath for use in Parts A and D.
1. Separate the hydroxide precipitates from the amphoteric hydroxides. To 2 mL
of the reference solution (in a small test tube) add 10 drops of 6 M NaOH (Caution!)
(see Dry Lab 4.A). Centrifuge and save the precipitate. Test for complete precipita-
tion (see Dry Lab 4.B) by adding several drops of 6 M NaOH to the supernatant.
Decant the supernatant into a small test tube and save for Part D.
2. Dissolve the hydroxide precipitates. Dissolve the precipitate with a minimum
number of drops of conc HNO3. (Caution: Be careful!) If necessary, heat the
solution in the hot water bath for several minutes.
1. Separate Fe³+ from Ni²tions. To the solution from Part A.2, add -5 drops of 4 M
NH₂Cl and then drops of conc NH, (Caution: Do not inhale-use a fume hood if
available) until the solution is basic to pH paper; add an additional 2 drops of conc
NH, to ensure the complexing of the Ni²+. Centrifuge, save the precipitate, and
transfer the supernatant to a small test tube for testing in Part C.
2. Confirmatory test. Dissolve the precipitate with 6 M HCl and add -5 drops of
0.1 M NH.SCNⓇ The blood-red solution due to the thiocyanatoiron (III) complex
confirms the presence of iron(III) ion in the test solution.
1. Confirmatory test. To the supernatant solution from Part B.1, add -3 drops of
dimethylglyoxime solution. Appearance of a pink (brick-red) precipitate con-
firms the presence of nickel ion in the test solution.
1. Separate Al³+ from Zn²+. Acidify the supernatant from Part A.1 to pH paper with
drops of 6 M HNO3. Add drops of 6 M NH, until the solution is now basic to pH
paper, then add -5 more drops. Heat the solution in the hot water bath for several
minutes to digest the gelatinous precipitate. Centrifuge and decant the
supernatant into a small test tube and save for the Zn²+ analysis in Part E.
2. Confirmatory test. Wash the precipitate (see Dry Lab 4.C) twice with ~1 mL of hot,
deionized water and discard each washing. Centrifugation is necessary after each
washing. Add drops of 6 M HNO3 until the precipitate just dissolves. Add -2 drops of
the aluminon reagent, stir, and add drops of 6 M NH3 until the solution is again basic
and a precipitate re-forms. Centrifuge the solution; if the Al(OH), precipitate is now
pink or red and the solution is colorless, then Al³+ is present in the sample.
1. Confirmatory test. To the supernatant from Part D.1, add drops of 6 M HCl until
the solution is acid to pH paper; then add -3 drops of 0.2 M K₁[Fe(CN)6] and stir.
A very-light-green precipitate confirms the presence of Zn²+ in the sample. The
precipitate is slow to form and difficult to see. Centrifugation may be necessary.
Disposal: Dispose of all test solutions and precipitates in the Waste Metal
Salts container.
CLEANUP: Rinse each test tube twice with tap water. Discard each rinse in the
Waste Metal Salts container. Thoroughly clean each test tube with soap and tap water;
rinse twice with tap water and twice with deionized water.
The qualitative analysis of inorganic cations and anions is a study in itself. If further
interest in the separation and identification of ions seems intriguing, research various
qualitative analysis schemes online. Complete textbooks are also written on the subject.
Transcribed Image Text:A. Separation of Ni²+ and Fe³+ from Zn²+ and Al³+ B. Test for Iron(III) Ion 17b 13b 11 11f C. Test for Nickel Ion E. Test for 17b Zinc Ion 13b D. Test for Aluminum Ion 17b The Next Step 11f To digest the precipitate: to make the precipitate more compact 11f The Experimental Procedure is written for a single reference solution. If you are simul- taneously identifying cations in both a reference solution and a test solution, adjust the procedure accordingly. If the test solution is a sample with an environmental origin, then gravity filter 10-15 mL before beginning the Experimental Procedure. Prepare the hot water bath for use in Parts A and D. 1. Separate the hydroxide precipitates from the amphoteric hydroxides. To 2 mL of the reference solution (in a small test tube) add 10 drops of 6 M NaOH (Caution!) (see Dry Lab 4.A). Centrifuge and save the precipitate. Test for complete precipita- tion (see Dry Lab 4.B) by adding several drops of 6 M NaOH to the supernatant. Decant the supernatant into a small test tube and save for Part D. 2. Dissolve the hydroxide precipitates. Dissolve the precipitate with a minimum number of drops of conc HNO3. (Caution: Be careful!) If necessary, heat the solution in the hot water bath for several minutes. 1. Separate Fe³+ from Ni²tions. To the solution from Part A.2, add -5 drops of 4 M NH₂Cl and then drops of conc NH, (Caution: Do not inhale-use a fume hood if available) until the solution is basic to pH paper; add an additional 2 drops of conc NH, to ensure the complexing of the Ni²+. Centrifuge, save the precipitate, and transfer the supernatant to a small test tube for testing in Part C. 2. Confirmatory test. Dissolve the precipitate with 6 M HCl and add -5 drops of 0.1 M NH.SCNⓇ The blood-red solution due to the thiocyanatoiron (III) complex confirms the presence of iron(III) ion in the test solution. 1. Confirmatory test. To the supernatant solution from Part B.1, add -3 drops of dimethylglyoxime solution. Appearance of a pink (brick-red) precipitate con- firms the presence of nickel ion in the test solution. 1. Separate Al³+ from Zn²+. Acidify the supernatant from Part A.1 to pH paper with drops of 6 M HNO3. Add drops of 6 M NH, until the solution is now basic to pH paper, then add -5 more drops. Heat the solution in the hot water bath for several minutes to digest the gelatinous precipitate. Centrifuge and decant the supernatant into a small test tube and save for the Zn²+ analysis in Part E. 2. Confirmatory test. Wash the precipitate (see Dry Lab 4.C) twice with ~1 mL of hot, deionized water and discard each washing. Centrifugation is necessary after each washing. Add drops of 6 M HNO3 until the precipitate just dissolves. Add -2 drops of the aluminon reagent, stir, and add drops of 6 M NH3 until the solution is again basic and a precipitate re-forms. Centrifuge the solution; if the Al(OH), precipitate is now pink or red and the solution is colorless, then Al³+ is present in the sample. 1. Confirmatory test. To the supernatant from Part D.1, add drops of 6 M HCl until the solution is acid to pH paper; then add -3 drops of 0.2 M K₁[Fe(CN)6] and stir. A very-light-green precipitate confirms the presence of Zn²+ in the sample. The precipitate is slow to form and difficult to see. Centrifugation may be necessary. Disposal: Dispose of all test solutions and precipitates in the Waste Metal Salts container. CLEANUP: Rinse each test tube twice with tap water. Discard each rinse in the Waste Metal Salts container. Thoroughly clean each test tube with soap and tap water; rinse twice with tap water and twice with deionized water. The qualitative analysis of inorganic cations and anions is a study in itself. If further interest in the separation and identification of ions seems intriguing, research various qualitative analysis schemes online. Complete textbooks are also written on the subject.
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