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ph

Posted: Thu Jan 16, 2020 5:45 pm
by annikaying
Can ph be above 14 or below 0? Or is there a specific cap at those values?

Re: ph

Posted: Thu Jan 16, 2020 5:47 pm
by Connor Chappell 2B
THe scale is not restricted between 0 and 14 for pH or pOH. However, at room temperature, this scale is restricted. This is because the value of kw (autoprolysis of water) is 10^-14 and thus, the maximum valuue is set to be 14, with the lowest value being 0. In many of the cases, we are assuming that the reaction is at room temperature.

Re: ph

Posted: Thu Jan 16, 2020 5:49 pm
by Ruby Tang 2J
Yes! pH can definitely be above 14 or below 0. An example is 12 M HCl, which has a pH of about -1.08. If we consider mathematically that pH=-log[H+], then we know that if [H+] is greater than 1, pH has to be below 0.

Re: ph

Posted: Thu Jan 16, 2020 6:43 pm
by Hailey Kim 4G
Yes, the pH can be less than 0 and greater than 14; however, is it more likely for the pH to fall in the 0-14 range.

Re: ph

Posted: Thu Jan 16, 2020 8:50 pm
by Megan Kirschner
The way I like to think of it is it can lie outside of the 0 to 14 range, but pH + pOH must equal 14 when added together.

Re: ph

Posted: Fri Jan 17, 2020 12:56 pm
by smurphy1D
when trying to find the pH or poH of something, do We take the - log of the opposite concentration of the one we are trying to find?

Re: ph

Posted: Fri Jan 17, 2020 3:39 pm
by MinuChoi
when trying to find the pH or poH of something, do We take the - log of the opposite concentration of the one we are trying to find?

No; pH = -log[H+] and pOH=-log[OH-].
But you can use pH to find pOH and vice versa because pH + pOH = 14.

Re: ph

Posted: Sun Jan 19, 2020 4:59 pm
by Manav Govil 1B
The pH scale is not restricted per se, but it is at room temp. I don't think that they will ever ask you a question where the answer is pH 15.45 though. Oh, and pH can never be negative.

Re: ph

Posted: Sun Jan 19, 2020 6:44 pm
by kausalya_1k
i believe that it's possible, but for the scope of this class i don't think we don't need to worry about that

Re: ph

Posted: Sun Jan 19, 2020 7:01 pm
by Areena H 2K
I believe the ph can be above or below 14 but generally, the range it falls under is 0-14

Re: ph

Posted: Sun Jan 19, 2020 8:25 pm
by preyasikumar_2L
At different temperatures, the pH scale can go beyond the standard 0 to 14, because at different temperatures the autoprotolysis value of water is different from 10-14, but we do not need to worry about this in this class (for now).