Chemistry: [ Iodine ], 快來教我!

2006-11-07 1:12 am

書到話 iodine 唔同 state 有唔同 colour.
--iodine solid is purple
--iodine vapour is purple
--iodine solution is brown ( 但係 iodine is soluble 咩? )

***1. 點解會咁既? 乜佢地既formula唔係都係 I2 咩??

咁electrolysis時, eg. KI ( potassium iodide )
2I- → I2 + 2e-
***2. 咁呢到個 colour change係 colourless to what?? to BROWN or PURPLE??

更新1:

仲有! electrolysis時, eg. molten lead(II) iodide, ***3. 咁呢到個 colour change係 from what to what (to BROWN or PURPLE?) ?

回答 (2)

老爺子

2006-11-08 12:21 pm

✔ 最佳答案

The solubility of iodine in water is extremely low and some CE text books state that iodine is insoluble in water. In aqueous iodine, the electrons in iodine molecule interact with the electrons in water molecule. Such electron interactions make the solution very pale yellow.

However, iodine is very soluble in KI solution, and the soluble is deep brown due to the presence of I3^- ions.

In electrolysis of molten KI or molten PbI2, purple iodine vapour is formed at the anode.

In electrolysis of aqueous KI solution, brown iodine solution is formed at the cathode.

參考: memory

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殿居男

2006-11-07 7:53 pm

when iodine exist the diatomic structure is mostly in puple color
but the Iodine in solution is not in I2 form
the I2 will form a complex ion with iodide form I3- which is borwn in colour.

as the molten lead(II) iodide electrolysis iodine vapour will be formed ----- purple colour but the high temperature the iodine in gaseous state

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