ph


Moderators: Chem_Mod, Chem_Admin

annikaying
Posts: 94
Joined: Sat Sep 14, 2019 12:16 am

ph

Postby annikaying » Thu Jan 16, 2020 5:45 pm

Can ph be above 14 or below 0? Or is there a specific cap at those values?

Connor Chappell 2B
Posts: 59
Joined: Wed Feb 20, 2019 12:16 am

Re: ph

Postby Connor Chappell 2B » Thu Jan 16, 2020 5:47 pm

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.

Ruby Tang 2J
Posts: 102
Joined: Fri Aug 30, 2019 12:15 am

Re: ph

Postby Ruby Tang 2J » Thu Jan 16, 2020 5:49 pm

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.

Hailey Kim 4G
Posts: 110
Joined: Sat Jul 20, 2019 12:16 am

Re: ph

Postby Hailey Kim 4G » Thu Jan 16, 2020 6:43 pm

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.

Megan Kirschner
Posts: 46
Joined: Wed Feb 20, 2019 12:17 am

Re: ph

Postby Megan Kirschner » Thu Jan 16, 2020 8:50 pm

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.

smurphy1D
Posts: 51
Joined: Mon Nov 18, 2019 12:18 am

Re: ph

Postby smurphy1D » Fri Jan 17, 2020 12:56 pm

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?

MinuChoi
Posts: 100
Joined: Wed Sep 18, 2019 12:15 am

Re: ph

Postby MinuChoi » Fri Jan 17, 2020 3:39 pm

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.

Manav Govil 1B
Posts: 104
Joined: Sat Sep 07, 2019 12:19 am

Re: ph

Postby Manav Govil 1B » Sun Jan 19, 2020 4:59 pm

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.

kausalya_1k
Posts: 50
Joined: Wed Nov 14, 2018 12:23 am

Re: ph

Postby kausalya_1k » Sun Jan 19, 2020 6:44 pm

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

Areena H 2K
Posts: 81
Joined: Wed Dec 05, 2018 12:18 am

Re: ph

Postby Areena H 2K » Sun Jan 19, 2020 7:01 pm

I believe the ph can be above or below 14 but generally, the range it falls under is 0-14

preyasikumar_2L
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

Re: ph

Postby preyasikumar_2L » Sun Jan 19, 2020 8:25 pm

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).


Return to “Ideal Gases”

Who is online

Users browsing this forum: No registered users and 0 guests