kclo4 - 28-1-2005 at 20:47
When sodium hydroxide is add to super saturated salt (NaCl) water it kicks out the salt how is this possible isn’t salt more soluble then NaOH?
Darkfire - 28-1-2005 at 22:08
I think NaOH is more soluble, as it will turn to mush if left exposed to open air, from absorbing water. I dont know if sodium hydroxide has a
definate crystal structure and NaCl has a definate one which made help it crystalise out of the solution.
...But my best guess to explain this would be that since NaCl has the higher consentration in the solution it will be the one to ppt out first. Id
assume a super saturated solution of NaOH would ppt NaOH as NaCl was added,
kclo4 - 28-1-2005 at 22:35
When the salt falls out it is not in a crystal
Darkfire - 28-1-2005 at 22:53
Yes it is.
Synopsis - 28-1-2005 at 23:02
It might come out as an amorphous powder rather than as a crystal, and probably will. Actually, I doubt you precipitate pure NaCl from this procedure,
more a mixture of NaCl and NaOH. When you add a cation (or anion) that is already saturated in solution, it will precipitate with the counteranion (or
coutercation) that is readily available at this moment. In this case, this means either Cl- or HO-.
Darkfire - 28-1-2005 at 23:34
The powder is just small crystals. They dont have time to grow huge.
kclo4 - 28-1-2005 at 23:45
is there any way to test for nacl crystals
Darkfire - 28-1-2005 at 23:56
Toss it in some h2so4, if HCl is evolved its NaCl if not its NaOH. A titration would be a safer method.
kclo4 - 28-1-2005 at 23:58
i mean to see if it was in crystal form
Synopsis - 29-1-2005 at 10:00
The powder might not be crystalline. It indeed is an *ionic solid*, but not necessary a crystal. I never saw NaOH in crystalline form, and I played
with many kilogram of the stuff in flake, pellet and powder form.
A crystal is, by definition, a pure substance with 3d positional order. When unpure or when 3d positional order is not met, it only can be a amorphous
compound.
garage chemist - 29-1-2005 at 10:21
Look at it with a microscope, then you can see if the particles are crystals or if they are irregular and without sharp corners (then they are
amorphous).
Large NaCl crysals can be made by slowly evaporating a saturated NaCl soln, if crystals are what you want.
[Edited on 29-1-2005 by garage chemist]
kclo4 - 30-1-2005 at 13:49
In NaOH solution the salt dose not make the NaOH to ppt out