IN my experiment, I was doing a qualitative analysis of Group I and II anions using a flowchart. IN the chart I added 5 drops of 0.1M AgNO3 and several drops of 3M HNO3 to 5 drops of solution and found that a precipitate was formed. Thus it was classified as a Group I anion. Next, to 5 drops of fresh sample I added 5 drops of 0.1 M AgNO3 and observed a precipitate once again. Then I centrifuge the solution and discarded the liquid. Then I added 1mL concentrated NH4OH and 1mL water and stirred well. I once again observed another precipitate and then to 3 drops of fresh sample, add 3M HNO3 until just acidic. Add 3 drops of NaOCl solution and then 1mL hexane. Then I had to observe the color of the hexane layer. If it turned yellow it was Br- and if it was brown or purple then it was I-.
My question is: What is going on in the hexane layer at the end of the Group I anion experiment?
The NaOCl has oxidized any bromide or iodide in the unknown to free bromine (the element) or free iodine (the element) respectively. Neither bromine nor iodine are appreciably soluble in water but they are quite soluble in hexane (hexane is a non-polar solvent and bromine and iodine are non-polar elements while water is a polar solvent). The yellow color (if it is bromine) and the violet color (if iodine) are caused by London dispersion forces (instantaneous dipole-induced dipole) between Br or I atoms since these are the only forces acting in the non-polar solvent. (The black color for I2 PROBABLY is the result of a large excess of I2 and the violet color can look almost black if it is very intense).I hope this explanation is what you are looking for. By the way, in this particular question I could tell what was going on; however, not all qualitative schemes are the same and sometimes it is helpful if we know what anions are in group I. It is interesting to me that you are doing a qual run on ANIONS. I did several runs on Groups I, II, III, IV, and V of anions (in addition to the usual group I thorough V of cations. But later years have seen the decline of anion analyses, almost to the point of extinction. I'm glad to see it coming back. There's a lot of good chemistry in anion qual tests.
The Group I anion has been oxidized to its molecular form: Br2 or I2 in the earlier steps. When you shake two layer mixture, the molecular (as opposed to ionic) Br2 or I2 are extracted into the hexane layer and give it the characteristic color or of one of those molecular forms.
Well, in the hexane layer, it's like a little party going on! The hexane is like the dance floor, and the anions Br- and I- are the party animals trying to show off their colors.
If the hexane layer turns yellow, then it means that the anion Br- is having a blast and showing off its vibrant yellow outfit. It's like Br- is saying, "Hey, look at me, I'm the life of the party!"
But if the hexane layer turns brown or purple, then it's the anion I- who's stealing the show. I- is like, "Move aside, yellow, because I'm here to make a bold statement with my brown or purple attire!"
So, in summary, the color of the hexane layer at the end of the Group I anion experiment is like a fashion show where the anions Br- and I- are strutting their stuff and trying to outshine each other. It's a colorful competition, my friend!
In the hexane layer at the end of the Group I anion experiment, a color change is observed depending on the type of anion present in the sample.
If the hexane layer turns yellow, it indicates the presence of bromide ions (Br-). On the other hand, if the hexane layer turns brown or purple, it indicates the presence of iodide ions (I-).
In the hexane layer at the end of the Group I anion experiment, a color change is being observed. This color change indicates the presence of either Br- (bromide ion) or I- (iodide ion) in the solution.
To understand this, let's go through the steps leading up to the hexane layer:
1. The initial steps of the experiment involve adding AgNO3 and HNO3 to a sample, resulting in the formation of a precipitate. This indicates the presence of Group I anion.
2. In the next step, the solution is centrifuged to separate the solid precipitate from the liquid. The liquid is then discarded.
3. Then, 1mL of concentrated NH4OH (ammonium hydroxide) and 1mL of water are added to the sample, followed by stirring. This step helps to further separate and identify the specific anion present.
4. A precipitate is observed once again, indicating the presence of the Group I anion.
5. Now, to observe the color change in the hexane layer, 3 drops of the fresh sample are taken and 3M HNO3 is added until the solution becomes just acidic. This step is done to ensure that the sample is at the correct pH for the subsequent reactions.
6. Following that, 3 drops of NaOCl (sodium hypochlorite) solution are added to the sample. This reagent helps to oxidize bromide (Br-) and iodide (I-) ions.
7. Finally, 1mL of hexane is added to the solution and mixed. Hexane is an organic solvent that forms a separate layer from the aqueous solution. The organic layer (hexane layer) now contains any organic compounds that have been extracted from the aqueous solution.
The color change observed in the hexane layer is due to the formation of an organic complex between the oxidized form of the anion and the hexane solvent. If the color of the hexane layer turns yellow, it indicates the presence of Br-, while brown or purple color suggests the presence of I-. This color change occurs because the bromide and iodide ions interact with the hexane solvent to form different-colored complexes.
In summary, the color change observed in the hexane layer in the Group I anion experiment is used as an indication of the presence of either Br- or I- in the sample, based on the observed color.