Exploring the Color Changes of CoCl2 and Co in Solution

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In summary, there are three cases discussed in the conversation: solid CoCl2, CoCl2 solution, and plain Co in solution. It is mentioned that CoCl2 goes from blue to pink with water and the reverse occurs with HCl solution. It is also noted that both Co and CoCl2 produce a pink color in solution with water due to the formation of different complex ions, and adding HCl converts the solution back to blue. The conversation also mentions the solubility of Co in water and the formation of [Co(H2O)6]2+ and [CoCl4]2- ions. The expert is seeking further information on the complex ions responsible for the colors in each case.
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Big-Daddy
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I have heard, quite simplistically, that "CoCl2 goes blue to pink with water" and "the reverse occurs with HCl solution". I have also heard that Co, and CoCl2, are pink in solution with water (in both cases with a different complex ion formed), and in both cases adding HCl again turns the solution blue.

So there are three cases: solid CoCl2, CoCl2 solution, and plain Co in solution. In each case I will need to know which complex ions are responsible for each colour produced.

The Internet has helped but I can't find out more from it than I already have, which is that Co2+ immediately forms [Co(H2O)6]2+ in solution, which is responsible for the pink colour, and that adding Cl- ions (e.g. HCl solution) then converts this to the blue [CoCl4]2- ion. So the plain Co in solution case is solved.

But what happens in the other two cases?
 
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with Co being a metal, are you sure that it is soluble in water?
 

1. What is the purpose of exploring the color changes of CoCl2 and Co in solution?

The purpose of this experiment is to observe and understand the relationship between the color changes of cobalt chloride (CoCl2) and cobalt (Co) in solution, and their corresponding chemical reactions.

2. What materials are needed for this experiment?

The materials needed for this experiment include cobalt chloride (CoCl2), cobalt (Co), distilled water, test tubes, a test tube rack, a dropper, and a source of heat (such as a Bunsen burner or hot plate).

3. What are the steps involved in the experiment?

The steps involved in the experiment are: 1) preparing a solution of cobalt chloride, 2) heating the solution to observe the color change, 3) adding cobalt metal to the solution and observing the color change, and 4) repeating the process with varying amounts of cobalt metal to observe the effect on the color change.

4. What causes the color changes in CoCl2 and Co in solution?

The color changes in CoCl2 and Co in solution are caused by the formation of different complexes. When heated, CoCl2 forms a pink-colored complex, while the addition of cobalt metal forms a blue-colored complex. The difference in color is due to the different ligands that bind to the cobalt ion.

5. What are the applications of studying the color changes of CoCl2 and Co in solution?

Studying the color changes of CoCl2 and Co in solution has various applications in chemistry, including identifying unknown compounds, understanding complex formation, and determining the concentration of ions in a solution. It also has practical applications in industries such as pharmaceuticals, where the color changes can indicate the completion of a chemical reaction.

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