madmanhere - 7-3-2012 at 22:55
According to Wikipedia, NaOH has a solubility of 1110g/L in water at 20'C. If I dissolve 1.1kg of NaOH pellets in 1L H2O, calculation of pH is as
follows:
1.1kg NaOH = 1110/40 = 27.75 mol
=27.75 mol/ L
pOH= -log 27.75
pH + pOH=14
pH = 14 + log 27.75
= 15.44
pH > 14!!! What am I doing wrong?
[Edited on 8-3-2012 by madmanhere]
bbartlog - 7-3-2012 at 23:05
I don't think there's any theoretical reason why you can't have a pH above 14. Or below zero for that matter.
madmanhere - 7-3-2012 at 23:10
You mean to say that although 1.1kg can dissolve, only a small portion of it will dissociate and the rest will exist as undissociated NaOH?
bbartlog - 7-3-2012 at 23:30
Uh, no. That's like the opposite of what I'm saying. Your calculation looks good, the NaOH is almost entirely dissociated, and the pH is 15+. So
what's the problem? Did someone tell you that pH can only be in the range of 0-14 or something?
zoombafu - 7-3-2012 at 23:43
I'm pretty sure your calculations are correct. And yes pH can go above and below the normal 0-14 range
source: http://books.google.com/books?id=eKtNUN1FeqEC&lpg=PA3&dq=pH%20above%2014&pg=PA3#v=onepage&q=pH%20above%2014&f=false
madmanhere - 8-3-2012 at 03:43
I didn't know pH could go higher than 14. My bad.
Thanks guys. 