Chemical Magic 5# Behind Unchanged of Purple Color

jamhuery (61)in #science • 7 years ago (edited)

Hello dear steemian, Hopefully, everybody still health to read my post in steemit, in this opportunity I wanna share you something about a magic base on chemical science.

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In the past, the people mentioned alchemy as magic or a science mixed with magic, because the chemistry process can change the material in a way doesn't make sense (if we don't know about it). If only water mixed with the red syrup, then the water color will turn to red, or burning an object should to use a matches, this is reasonable. What if the colored liquid mixed with clear liquid? but the result remains clear liquid. Does this make sense? Chemistry Explain You.... The chemistry sometime look like an magic but certainly it is a science.

Do You Know H₂O₂?

H₂O₂ or Hydrogen Peroxide is a strong oxidizer that has clear liquid color with chemical formula H₂O₂, it used in the bleaching industry because it doesn't leave harmful residues while it been reacting and friendly environmental, hydrogen peroxide produced by reacting Hydrogen with Oxygen (O₂). In the pulp industry, H₂O₂combined with NaOH (soda ash) to increase rate decomposition. And Hydrogen Peroxide also used in rocket fuel industry.

Iodine with chemical formula I₂ is a solid material has dark purple color, iodine usually used as a wound medicine (for example Betadine in Indonesia), it was difficult to dissolve in water or takes long time to make it dissolve into water, so that in the iodine dissolution we should use potassium iodide (KI) to accelerate solubility.

If the coffee mixed with water then the color will turn to black, but if iodine mixed with hydrogen peroxide, What color will happen? . . . . . . certainly clear color.

You can watch this video

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Chemistry Explain

As I explained above, the hydrogen peroxide is a strong oxidizer agent, oxidation is a change of increasing of oxidation number, whereas oxidizer is decrease of oxidation number of an atomic compound. So the term of oxidizer refers to a compound not on an atom. Why color remains clear when iodine mixed with hydrogen peroxide ?

Actually, this process is an iodometric titration, Where this titration requires an indicator, because the end point of a titration shows the color change, when the titration has not reached the end point the color remains unchanged, when a solution has stabilized and the titration point has reached the end point , the color will not disappear even in stir because the solution is stable. We can create a reaction formula both H₂O₂ and I₂ as follow :

H₂O₂ + 2H⁺ + 2^e- ⇒ 2H₂O

2I^- ⇒ I₂ + 2^e-

Forming of Iodide

H₂O₂ + 2H⁺ + 2I^- ⇒ I₂ + 2H₂O

H₂O₂ + 2HI ⇒ I₂ + 2H₂O

The color change of the solution is an indication of exhaustion of thiosulfate ion, so the reaction between hydrogen peroxide and thiosulfate has an equivalent value, so the hydrogen peroxide can determine the residual of thiosulfate, in this reaction iodide acts as a reducing agent, iodide acid formed by acidification of potassium iodide (KI), the forming of iodine is the result of reaction with sodium thiosulfate (Na₂S₂O₃), the color change doesn't occur because thiosulfate hasn't been reacted, if thiosulfate has reacted then the solution will turn to purple color. Essentially, the function of sodium thiosulfate is to keep the iodine free in the solution, so the color won't to change.

Because the Hydrogen Peroxide (H₂O₂) can not be titrated directly with thiosulfate, so it should firstly e reacted with Potassium Premanganate (KMnO₄), The mole ratio of reaction can determine the equivalent both hydrogen peroxide and thiosulfate ion, where the hydrogen peroxide in this reaction acts as reducing agent that oxidized by Potassium (KMnO4), this reaction is first-order reaction which the rate of reaction depends on one reactant, it is the concentration of hydrogen peroxide and then its solution was unstable because hydrogen peroxide can decompose into hydrogen and oxygen, chemically the reaction can be formulated

2MnO₄^– + 5H₂O₂ + 6H⁺ ⇒ 2MN²⁺ + 5O₂ + 8H₂O

In this reaction potassium permanganate (KMnO4) acts as a primary solution, and hydrogen peroxide acts as a secondary solution. The potassium (KMnO4) expressed as a tritator in this reaction. At beginning of the process, the solution from colorless becomes colored (Purple).

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Conclusion

Iodometric titration is a method of quantitative determination of iodine with a sample or a substance which has a lower oxidation potential than iodine, so the substance can be oxidized. The color change of solution is an indication of thiosulfate exhaustion, or thiosulfate keeps the iodine free in the solution, so the color won't to be change.