Sciencemadness Discussion Board

NaOh or KOH

octaimelda - 22-4-2012 at 18:20

Which is have the larger solubility in organic solvent, NaOH or KOH?? Thank You, guys. hehe . :)

barley81 - 22-4-2012 at 19:01

KOH. It is more soluble in ethanol than NaOH, and its lower lattice energy should allow for higher solubility in other organic solvents.

octaimelda - 22-4-2012 at 19:29

why?? is it have the relationship about its base or the bond with -OH??

woelen - 22-4-2012 at 22:13

From the point of view of alkalinity (the base) both NaOH and KOH are very similar. Equal molarity of solutions of these mean equal alkalinity (equal pH). Both are strong bases.

Coordination of the OH(-) ion to the solvent also is the same for both compounds. So, the difference is not from any of the two things you mentioned.

It is the solid phase (NaOH vs. KOH) which makes the difference. In KOH, the ions K(+) and OH(-) are somewhat more loosely "connected" to each other than Na(+) and OH(-) in NaOH and hence the solid more easily breaks up in its constituent ions.

AJKOER - 23-4-2012 at 06:51

A possible example of the more loose connected nature of KOH over NaOH (in which the Potassium salt appears to be preferred) is the creation of Cl2O by treating an aqueous solution of Potassium hypochlorite with Chlorine:

1. Cl2 + KClO --H2O--> KCl + Cl2O

Source: "The Chemical Elements and their Compounds", by N.V. Sidgwich, Vol. 2, Page 1201 (in library).

I would note that:

2. KClO + H2O <----> KOH + HOCl

So, I think it is instructive to view the reaction as:

3. Cl2 + KOH + HOCl --> KCl + H2O + Cl2O

Apparently, under certain conditions, the reaction [1] has been cited to proceed in the opposite direction (implying reversible). To quote:

HOCl + KCl --> ‘’KOH’’ + Cl2
Cl2O + H2O --> 2HOCl

Source: http://enac2.epfl.ch/web/doctorants/2004/612.pdf

Note, in cold dilute solutions with excess NaOH, for example:

4. 2 NaOH + Cl2 = NaCl + NaOCl + H2O

(see, for example: https://docs.google.com/viewer?a=v&q=cache:vKvH-lo0mvkJ:... )

which is basically reaction [1] in which the Cl2O (or HOCl) has been neutralized.

For the record, preparation of Cl2O in the laboratory is most often cited via HgO, and commercially, paths proceed with Chlorine and steam acting on NaOH or Na2CO3 or NaHCO3.


[Edited on 23-4-2012 by AJKOER]

woelen - 23-4-2012 at 22:33

I see no relation to the rest of this thread. We are talking about dissolving solid KOH. What you are talking about are aqueous solutions and for such it does not matter whether we have the sodium salt or the potassium salt. The reactions of the chlorine and the anionic species are the same, regardless of the counterion being sodium or potassium.

cazruto - 24-4-2012 at 01:01

however KOH is good, i have one question i need dissolved KOH in organic solution but not use -OH group its problem for me please help me

Quote: Originally posted by woelen  
From the point of view of alkalinity (the base) both NaOH and KOH are very similar. Equal molarity of solutions of these mean equal alkalinity (equal pH). Both are strong bases.

Coordination of the OH(-) ion to the solvent also is the same for both compounds. So, the difference is not from any of the two things you mentioned.

It is the solid phase (NaOH vs. KOH) which makes the difference. In KOH, the ions K(+) and OH(-) are somewhat more loosely "connected" to each other than Na(+) and OH(-) in NaOH and hence the solid more easily breaks up in its constituent ions.

woelen - 24-4-2012 at 02:14

Please elaborate more on it. Your question is not clear. You want KOH dissolved, but do not want OH(-) ions?

DJF90 - 24-4-2012 at 02:51

I think he means KOH in a non-hydroxylic organic solvent. My suggestion is to use something like toluene and 18-crown-6 or TBAB. I use this routinely and the hydroxide species under these unsolvated conditions has a pK of about 30 (rough estimate)