I would like to understand when the water is boiled only pure vapor is produced and ions do not exist with vapor. Why?

Can't the ions stick to water vapor?


Are Na+ and Cl- have boiling points? Why do they not evaporate?

  • 2
    $\begingroup$ Vaporisation involves a molecule dehydrating. The hydration free energy of Na and Cl is something like $10\times$ that of a water molecule. $\endgroup$
    – lemon
    Dec 14, 2018 at 16:24
  • $\begingroup$ This answer here chemistry.stackexchange.com/questions/31932/… shows how the ions are "bound" by H2O $\endgroup$
    – anna v
    Dec 14, 2018 at 18:22
  • $\begingroup$ I believe you can see salt evaporating from the sea level, on a windy day. It seems to keep close to the surface though. $\endgroup$ Dec 14, 2018 at 21:08

1 Answer 1


The ionic bond between sodium and chlorine ions is way stronger than the dipole-dipole interaction between water molecules. As a result, sodium chloride has much higher melting and boiling point than the boiling point of water.

So, sodium chloride does not vaporize at 100 degree centigrade under normal pressure.

  • 3
    $\begingroup$ But NaCl is not solid at the water. It's Na+ and Cl- $\endgroup$
    – MENG
    Dec 14, 2018 at 16:18
  • $\begingroup$ You cannot vaporize an isolated Na$^+$. It must take one Cl$^-$ with it. Once it leaves the water phase and goes into the vapour, it will solidify. This indecent can indeed happen as some ions will have enough kinetic energy (due to Maxwell-Boltzmann distribution) to leave the water liquid phase. $\endgroup$ Dec 14, 2018 at 16:28
  • $\begingroup$ But NaCl is not solid at the water. It's Na+ and Cl- – The sodium cations and chloride anions in solution are hydrated: i.e. they are surrounded by a mantle of water. What's more, the hydrated ions still interact, that is attract each other. Your view of a solution is risibly simple. Read up about watery, ionic solutions, ionic strength and such like. $\endgroup$
    – Gert
    Dec 14, 2018 at 16:39
  • 1
    $\begingroup$ @ArchismanPanigrahi You can absolutely evaporate a charged ion. It happens all the time in my simulations. $\endgroup$
    – lemon
    Dec 14, 2018 at 16:59
  • 2
    $\begingroup$ @Gert NaCl has a solubility product of about 40, I can't see how Na-Cl interactions are relevant here... $\endgroup$
    – lemon
    Dec 14, 2018 at 17:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.