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Renee Grange 1I
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Postby Renee Grange 1I » Thu Jan 16, 2020 1:31 pm

When do we need to take into account the autoprotolysis of water needs to be taken into account?

Hannah Lee 2F
Posts: 117
Joined: Thu Jul 11, 2019 12:15 am

Re: Autoprotolysis

Postby Hannah Lee 2F » Thu Jan 16, 2020 1:45 pm


The autoprotolysis of water can be used to link the concentrations of H3O+ and OH- in an aqueous solution via the autoprotolysis constant, Kw. Because Kw is essentially an equilibrium constant, if [H3O+] increases due to acid being added into a solution, [OH-] must decrease in order to keep Kw the same, and vice versa, producing the equation: [H3O+][OH-] = Kw = 10^-14. (You can exclude H2O from the constant because it is basically a pure liquid, and its concentration does not change in any measurable way.

In a similar fashion, Kw links pOH and pH in an aqueous solution in the equation pH + pOH = 14 (which you can find by taking the negative log of the previous equation).

Sukanya Mohapatra 2G
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Re: Autoprotolysis

Postby Sukanya Mohapatra 2G » Thu Jan 16, 2020 3:29 pm

If the concentration from the addition of an acid is very small, then it will not affect the pH that much. So autoprotolysis will be the determining factor in the pH.

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