You are assigned an unknown solution that contains Group III cations. To -1 mL of this solution was added 6 M NH3 the solution was agitated to mix well, and a reddish-brown precipitate with a gelatinous solid clinging to the inner walls of the test tube was observed. The solution was centrifuged and the supernatant was tested for completeness of precipitation by adding an additional drop of 6 M NH3. No cloudiness was observed as the drop of reagent diffused through the solution. The supernatant was then carefully decanted into a clean test tube, labeled (1st solution), and saved for further testing later. The precipitate remaining in the test tube was washed with a small amount of water, centrifuged, and the wash decanted and discarded. To the precipitate was added about 10 drops of 6 M NAOH plus ~1 mL H20 and the test tube was vigorously agitated. The resulting suspension was centrifuged and the supernatant liquid was transferred to another clean test tube and clearly labeled (2nd solution). To the precipitate in the test tube several drops of 6 M HCI was added and mixed thoroughly dissolving the precipitate. Water was added to dilute the solution and the solution was mixed well to make it homogeneous. This was followed by the addition of a couple of drops of the reagent 0.1 M KSCN with mixing. The resulting solution turned blood red. Returning to the 2nd solution, 6 M HCI was added with agitation until the solution was acidic to litmus (blue to red). This was followed by adding a small excess of HCI. Two or three drops of the reagent aluminon was added plus -1 mL H20 and mixed well. The addition of 6 M NH3 followed until the solution was just basic to litmus. The solution was mixed well and upon standing for a few minutes a flocculent red precipitate was observed throughout an essentially clear solution. Analysis was continued by taking about one half of the decantate (solution one) and adding about 4-5 drops of thioacetamide solution and mixing. The solution was placed in a water bath at ~60°C under the fume hood for a few minutes. After a short period of time cloudiness with a grey to black precipitate was observed in the test tube. Based on the observations and information provided, identify the ion(s) present in your unknown solution. Options Fe^3+ Al^3+ Zn^2+

You are assigned an unknown solution that contains Group III cations. To -1 mL of this solution was added 6 M NH3 the solution was agitated to mix well, and a reddish-brown precipitate with a gelatinous solid clinging to the inner walls of the test tube was observed. The solution was centrifuged and the supernatant was tested for completeness of precipitation by adding an additional drop of 6 M NH3. No cloudiness was observed as the drop of reagent diffused through the solution. The supernatant was then carefully decanted into a clean test tube, labeled (1st solution), and saved for further testing later. The precipitate remaining in the test tube was washed with a small amount of water, centrifuged, and the wash decanted and discarded. To the precipitate was added about 10 drops of 6 M NAOH plus ~1 mL H20 and the test tube was vigorously agitated. The resulting suspension was centrifuged and the supernatant liquid was transferred to another clean test tube and clearly labeled (2nd solution). To the precipitate in the test tube several drops of 6 M HCI was added and mixed thoroughly dissolving the precipitate. Water was added to dilute the solution and the solution was mixed well to make it homogeneous. This was followed by the addition of a couple of drops of the reagent 0.1 M KSCN with mixing. The resulting solution turned blood red. Returning to the 2nd solution, 6 M HCI was added with agitation until the solution was acidic to litmus (blue to red). This was followed by adding a small excess of HCI. Two or three drops of the reagent aluminon was added plus -1 mL H20 and mixed well. The addition of 6 M NH3 followed until the solution was just basic to litmus. The solution was mixed well and upon standing for a few minutes a flocculent red precipitate was observed throughout an essentially clear solution. Analysis was continued by taking about one half of the decantate (solution one) and adding about 4-5 drops of thioacetamide solution and mixing. The solution was placed in a water bath at ~60°C under the fume hood for a few minutes. After a short period of time cloudiness with a grey to black precipitate was observed in the test tube. Based on the observations and information provided, identify the ion(s) present in your unknown solution. Options Fe^3+ Al^3+ Zn^2+

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter31: Introduction To Analytical Separations

Section: Chapter Questions

Problem 31.18QAP

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