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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Faisal on March 02, 2008, 03:16:23 PM

Title: can pH or pOH ever be zero or negative?
Post by: Faisal on March 02, 2008, 03:16:23 PM

I was solving acid-base probs for my exam...I noticed in the answers "pH=-0.3"...which means pH can be negative.
But then there was a question where conc. of OH- was 1M.Therefore pOH=-log 1 which is 0.But in the answers it said "pOH=1 and pH=14"....how is that possible...isn't pH+pOH=14...1+14=15!!!
Any comments?

Title: Re: can pH or pOH ever be zero or negative?
Post by: Arkcon on March 02, 2008, 03:24:46 PM

Wikipedia has a fair explanation for very low pH values, some as low as -3.5, or even -5.  See: http://en.wikipedia.org/wiki/PH#Explanation

Though I would like to see the problem you've been given that gives a pH of -0.3, you might have made an error, given that the explanation for superacids and superbases implies they are non-ideal.

Title: Re: can pH or pOH ever be zero or negative?
Post by: Yggdrasil on March 02, 2008, 03:26:12 PM

Yes, pH can be negative if [H⁺] > 1M.

The second part is probably a typo.  If [OH^-] = 1M, then pOH = 0 and pH = 14.

Title: Re: can pH or pOH ever be zero or negative?
Post by: Faisal on March 02, 2008, 03:52:06 PM

ohk...Thank you very much