Auto Ionization of Water TBR Passage IX Acid Base

[MrNeuro]

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So i have a general question IF you are undergoing auto ionization and you find that the concentration of H+ is 1.0 x 10^-4 THEN the concentration of OH- must also be 1.0 x 10^-4 as

H2O + H2O ====> H3O+ + OH-

and your resulting pH=pOH and pH/pOH would equal 4 with pH +pOH = 8 instead of the normal 14

hence your Kw in this condition would be 10^-8 instead of 10^-14

keyword here being IF

I'm asking this just to verify what i got from the answer for #56 Passage IX Chapter 4 TBR Gen Chem

 

[chiddler]

Not far enough in chemistry to confidently say, but I thought pH + pOH =14

so if pH = 4, then pOH is 10.

So your initial premise of OH's concentration is incorrect I think.

 

[Pisiform]

Not far enough in chemistry to confidently say, but I thought pH + pOH =14

so if pH = 4, then pOH is 10.

So your initial premise of OH's concentration is incorrect I think.

i am confused ... is'nt that during auto-ionization both H+ and OH- has the same concentration. If any of them has a conc. of 10^-4 (not conventional 10^-7) as OP said, then I dont think it would be water anymore ... or atleast not water that is under auto-ionization ...

 

[Ssina]

yeah thats the point their are trying to make that not always pH + pOH= 14... other factors like temperature play a role in this as well... so hypothetically if we could auto ionize to get 10^-4 OH there should be the same amount of H+ and pH+pOH=8

 

[MrNeuro]

thanks for the input.

 

[MedPR]

So i have a general question IF you are undergoing auto ionization and you find that the concentration of H+ is 1.0 x 10^-4 THEN the concentration of OH- must also be 1.0 x 10^-4 as

H2O + H2O ====> H3O+ + OH-

and your resulting pH=pOH and pH/pOH would equal 4 with pH +pOH = 8 instead of the normal 14

hence your Kw in this condition would be 10^-8 instead of 10^-14

keyword here being IF

I'm asking this just to verify what i got from the answer for #56 Passage IX Chapter 4 TBR Gen Chem

Yea, this is what I got from that answer as well. I got it wrong because I assumed pH+pOH = 14. Reading the question carefully would've helped.