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I knew while learning about electrolysis that if the ionic compound is molten it becomes free moving ions.

If that is the case, what will happen if I continued heating till it reaches the boiling point so that the ionic compound evaporates?

Will it still be free moving ions?

Also, shouldn't the result be more efficient at electrolysis than in the liquid state due to increased mobility of ions? If not, why?

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The phase you describe is a plasma. –  Horba Nov 7 '12 at 12:07
I've incorporated your newer question into this one, they are nearly asking the same thing. –  ManishEarth Nov 19 '12 at 7:13
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3 Answers

up vote 10 down vote accepted

Usually not. Boiling point rarely exceeds 4-5 thousands kelvin. A typical ionic bound energy is about 5 eV. 1 eV is roughly 11 thousands kelvin, so ions in low-temperature vapors are in molecules. When temperature becomes enough to break ionic molecules, it is enough to strip one-two electrons from atoms, so hight-temperature vapors will be plasma with electrons and positive ions.

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I believe that gaseous ionic compounds such as NaCl are in fact diatomic NaCl. One can't create a plasma by simply boiling ordinary compounds. The forces between ions are way too strong.

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In liquid state, NaCl become free moving ions but the overall system is stable because of the attractions between the oppositely charged ions. I believe that gaseous NaCl would exists as very polar covalent or ionic molecules with their overall affect being electrically neutral (no plasma).

This is a purely intuited answer and should be taken with a grain of salt as I could find no numbers to back it up. If someone could change this into a comment for me I would be much obliged.

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