In the course of various qualitative analysis procedures, the following mixtures are encountered: (a) Zn 2+ and Cd 2+ . (b) Cr(OH) 3 and Fe(OH) 3 Suggest how each mixture might be separated.

Hey everyone today, we're being asked to identify which rages can be used to separate. And too many three plus and cobalt two plus in a solution. Now, before doing anything, we need to recall that even though it isn't explicitly stated in the question, we're dealing with cad ions that are dissolved in aqueous solutions, dissolved in aqueous solutions. And this is because only then will our soluble itty rules actually have any bearing on what re agents that we're using. So now we can go ahead and start looking at our agents. We'll start with the first one which is six smaller hydrochloric acid and we can actually rule this out. And this is because chlorine when reacting with um antimony or cobalt will form, let's write this out in green. It'll form either SB cl three or cobalt cl two. But because the chlorine isn't bonded to a silver lead or mercury, these will both be soluble salts. So they won't really be able to separate from one another. They'll both be soluble in solution, which means since one hasn't precipitated, we can't really separate them so we can rule the answer choice A off for answer choice B. However, and let's erase these for answer choice B. We're going to end up with two separate um products we're going to have S. P two, S three, Antoninus tri sulfide or C. O. S cobalt sulfide. Now the important thing to note here is that we're not just dealing with hydrogen sulfide is one of the reactant, we're also dealing with two molar hcl were in an acidic environment and due to the acidity due to our ability rules the Antoninus tri sulfide will actually end up being insoluble. It'll be insoluble in these acidic environments, but the cobalt sulfide will still be soluble At the Ph of eight, which means this indeed, is our answer choice. The sp three plus will end up precipitating out while the cobalt stays dissolved in solution, which means it is the easiest way for us to separate the two Catalans. Using the re agents hydrogen sulfide, two molar hydrochloric acid. I hope this helps. And I look forward to seeing you all in the next one.

Ch.17 - Additional Aspects of Aqueous Equilibria

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Brown 15th Edition

Ch.17 - Additional Aspects of Aqueous Equilibria

Problem 79a,b

Chapter 17, Problem 79a,b

In the course of various qualitative analysis procedures, the following mixtures are encountered: (a) Zn²⁺ and Cd²⁺. (b) Cr(OH)₃ and Fe(OH)₃ Suggest how each mixture might be separated.

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Identify the chemical properties of Zn^{2+} and Cd^{2+} ions, such as their solubility in different reagents.

Consider using a reagent that forms a precipitate with one ion but not the other. For example, sulfide ions (S^{2-}) can be used to precipitate CdS, which is insoluble, while ZnS is more soluble in acidic conditions.

Add a dilute acid to the mixture to ensure that ZnS remains dissolved while CdS precipitates out.

Filter the mixture to separate the solid CdS from the solution containing Zn^{2+}.

Wash and dry the precipitate to obtain pure CdS, and the remaining solution will contain Zn^{2+} ions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Solubility and Precipitation Reactions

Solubility refers to the ability of a substance to dissolve in a solvent, while precipitation reactions occur when two soluble salts react to form an insoluble compound. Understanding these concepts is crucial for separating ions in a mixture, as selective precipitation can be used to isolate specific ions based on their differing solubilities.

Complex Ion Formation

Complex ion formation involves the interaction of metal ions with ligands to form a stable complex. This concept is essential for separating metal ions like Zn2+ and Cd2+, as specific ligands can selectively bind to one metal ion over the other, allowing for their separation through techniques such as extraction or chromatography.

Ion Selectivity and Chromatography

Ion selectivity refers to the ability to preferentially separate ions based on their chemical properties. Chromatography is a technique that exploits these differences, allowing for the separation of Zn2+ and Cd2+ by passing the mixture through a medium that interacts differently with each ion, thus achieving separation based on their affinities.