Negative pH

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ASetlur_1G
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Negative pH

Postby ASetlur_1G » Sun Jan 26, 2020 11:26 pm

Why can the pH sometimes be negative? What's going on conceptually?

Angus Wu_4G
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Joined: Fri Aug 02, 2019 12:15 am

Re: Negative pH

Postby Angus Wu_4G » Sun Jan 26, 2020 11:33 pm

When the pH is negative, it just means that it is a very very very strong acid, and the H30+ concentration is extremely high. The pH level will be negative when you have a H30+ concentration greater than 1.0M. The pH range of 0-14 is only in general, there will be acids that can be less than zero pH, and there will be bases that are pH greater than 14.

christabellej 1F
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Joined: Sat Aug 17, 2019 12:17 am

Re: Negative pH

Postby christabellej 1F » Mon Jan 27, 2020 8:38 am

Usually the pH scale runs from 0 -14. However, it can sometimes have a negative pH if there is such a high concentration of hydronium ions that the pH of it becomes negative. I think these are called superacids.

Hannah Romeo 1J
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Joined: Thu Jul 11, 2019 12:16 am

Re: Negative pH

Postby Hannah Romeo 1J » Mon Jan 27, 2020 12:03 pm

Negative pH's can occur if the acid is so strong that the -log of the concentration of the hydronium ions in the solution results in a negative logarithm. This only occurs for super concentrated strong acids.

sarahforman_Dis2I
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Re: Negative pH

Postby sarahforman_Dis2I » Mon Jan 27, 2020 12:05 pm

ASetlur_1G wrote:Why can the pH sometimes be negative? What's going on conceptually?


If the concentration of H3O+ is greater than 1M, the pH will be 0 (if it is equal to 1) or negative. The reason that the scale is 1-14 is because in most systems, the concentration of H3O+ does not exceed 1M. Conversely, if the concentration OH- is larger than 1M, you can get a pH that is higher than 14. It is important to note that even though these situations are possible, they are not probable.

Tiffany_Chen 2K
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Joined: Fri Aug 30, 2019 12:15 am

Re: Negative pH

Postby Tiffany_Chen 2K » Thu Jan 30, 2020 2:31 pm

For very strong acids, their pH will be extremely low and can thus create a negative outcome using the log equation.

William Chan 1D
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Re: Negative pH

Postby William Chan 1D » Thu Jan 30, 2020 3:04 pm

pH is simply -log([H3O+]). When the molarity of H3O+ is higher than 1 M, then the pH will begin to become negative. Acids aren't typically this strong, and there's actually a special category for such strong acids called superacids, but they aren't common.

Ayushi2011
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Joined: Wed Feb 27, 2019 12:17 am

Re: Negative pH

Postby Ayushi2011 » Thu Jan 30, 2020 3:54 pm

Very strong acids have extremely low PH, sometimes it can be negative.

kennedyp
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Joined: Tue Nov 13, 2018 12:18 am

Re: Negative pH

Postby kennedyp » Thu Jan 30, 2020 4:56 pm

I remember the book saying that it's possible to have a negative pH or a pH higher than 14, but that they wouldn't ask us questions outside the scope of a pH value from 1-14. Any acid that has a concentration of hydrogen ions with a molarity greater than 1 will likely be calculated to have a negative pH.

Orrin Zhong 4G
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Joined: Sat Jul 20, 2019 12:16 am

Re: Negative pH

Postby Orrin Zhong 4G » Fri Jan 31, 2020 6:34 pm

Although the concentration of H+ ions cannot become negative, pH can become negative since pH = -log[H+]. Therefore, when the H+ concentration is greater than 1 M, the pH can become negative. However, we don't see negative pHs all that often because most reactions don't have H+ concentrations as high as 1 M.


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