/sci/ - Science & Math

>>6744655
bumpin

>>6744655
another bumperino

>>6744666
>666
>mfw

pH = pka - log (acid/base)

ka = 2e-9, nano-magnitude, it's a very weak-acid
pka = -log (2e-9) = 20.03, high pka

log (acid/base)
my guess is that it's not dissociated at all

>>6744673
What I thought too, basically the volume is too high and that means the conc is so minute. That in turn basically means there isn't enough acid to be properly neutralized.

>>6744655
http://chemwiki.ucdavis.edu/Physical_Chemistry/Equilibria/Le_Chatelier%27s_Principle/Ice_Tables

>>6744678
Anon I know how to do this, its how I found the pH.
What I am asking is what is wrong with this, and what needs to be added to fix it.

>>6744675
So you're suggesting that the acid is so dilute and the Ka is so small that Kw (the autoionization of water) is relevant?

Maybe so, it's been a long time since I've done a calculation like this.

>>6744686
Either that or the acid is so dilute it simply cannot be disassociated properly because there is too much water already in the solution.

>>6744675
I was thinking that Henderson Hasslebach works best under approximation conditions, whereas this case is an extremely dilute of an extremely weak acid

>>6744689
>there is too much water already in the solution.
yeah, this should be the right answer, water dissociation happens faster than this acid dissociating

>>6744673
I haven't done chemistry in 3 years; how do you get log (acid/base) from this problem? What's the acid and what's the base?

>>6744700
>faster
but this problem is thermodynamic, not kinetic

>>6744701
Hes doing it differently from me, but I did it like >>6744678 this process.

HOBr --> OBr- + H+
Initial concs:1 x 10-6 0 0
Change: -x +x +x
Equation:1 x 10-6 - x x x

Ka = Conc of Products/ Conc of Reactants
2x10^-9 = x^2/ 1 x 10^-6 - x
x value on the bottom is negligible when compared to the conc of HOBr, so it is ignored.
2 x 10^-9 x 1 x 10^-6 = x^2
x = 0.00000004472
pH = -log(Conc of H+)
pH = -log(0.00000004472)
pH = 7.349

>>6744655
can you fucking read cunt?

>>6744689
look at page 270 of this gen chem text
http://gen.lib.rus.ec/book/index.php?md5=C2A5E84AAE6B34145414FCFCC284608A

the section is titled
"Acid Solutions in Which Water Contributes to the H+ Concentration"

>>6744706
This is a discussion fuckwit. Its not homework, we are studying this for knowledge and were interesting in the answer because we couldn't figure it out on our own.

>>6744705
Cool, it all seems so familiar.

I may have to revisit all this shit again for that stupid standardized test to try apply for medicine to shut my parents up.

>>6744715
This stuff is really basic shit.

>>6744709
sure thing pal

pH is above 7, need to include H+ contribution from h2o

>>6744708
That link doesn't work for me for whatever reason. Can someone use it to explain what needs to be added? Is it volume?

>>6744726

>>6744732
>no tiffs

>>6744736
let me just upload the entire text to mega

>>6744738
https://mega.co.nz/#!2w0n3CjY!dcIRUKLTqYgjBZbQFDvCNa2Ks9HIWP-MmY1egqmRQ8Y
Zumdahl, 6th ed "Chemical Principles"