what is observed when cl gas reacts with KI paper?

Answer 1

I don't think that the above have actually seen this reaction, if they say that the paper goes violet.
Particularly if the paper is at all moist, it turns brown in the presence of chlorine. This is the colour of aqueous iodine.

Answer 2

Lancenigo di Villorba (TV), Italy

I have get many and many times the experimental procedure that you said.
I prepared an aqueous solutions of iodides with potato's starch.
The latter, as you know, give fastly a complex with iodine (e.g. I2) but does not with iodide (e.g. KI) salts...the complex is strongly coloured (blue-black hue) and this behaviour permit iodine's detection in trace even (e.g. high sensitivity reaction).
I add few drops ot this solution on a paper-piece. I cannot see a taint because the solution containts not iodine, hence it is colour-less.
In a tube, I mix bleach (e.g. NaClO), kitchen salt (e.g. NaCl), then I dilute for water addition. This done, I can add few drops of an acidic solution (Please!! Avoid nitric acid and other oxidizers!!).
I clean the "mouth-tube" by means of moist clothes and I conclude this operation with a second cloth wetted with a iodine solution (brown colour). In this way I remove any trace of oxidizers (e.g. used bleach) who can stand on mouth-tube.
Only now, I can lie my paper-piece on mouth-tube.
The liquid containt in the tube is a mixture who liberates chlorine (e.g. Cl2) bubbles, you yet know!
Since someone wrote yet about your question, I should see a purple or violet taint, following
2 KI + Cl2 ---> 2 KCl + I2
This is a merely application of redox theories, but in the practice you can see that if paper-piece is moist then violet hue rise toward a maximum and after it return colourless....
If paper-piece is moist then its water-containt can supports chlorine's action, thus it verify another reaction
I2 + 5 Cl2 + 6 H2O <----> 2 HIO3 + 10 HCl
Remember, many influence is governed by moist and chlorine' amount in your site's reaction (paper-piece).

I hope this helps you.

Answer 3

I have to agree with the above poster. This type of reaction is a specific redox reaction known as a halogen displacement reaction where a halogen will displace other halogens that are much lower in the group than itself (i.e. Fluorine will displace all other halogens but bromine can displace only iodine and astatine and not chlorine and fluorine.)

Answer 4

Chlorine is a fairly strong oxidising agent, so what will happen is that:

Cl2 + 2I- --> 2Cl- + I2

So, the KI paper should turn violet due to the production of I2.

Answer 5

Cl displaces Iodine from its salt, KI. IT has to do with its reduction potential.

So, KCl is formed, releasing violet iodine which stains the paper.

Cl2 + 2KI --------> 2Kcl + I2