## Autoprotolysis

Renee Grange 1I
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Joined: Fri Aug 30, 2019 12:16 am
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### Autoprotolysis

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

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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Joined: Sat Aug 17, 2019 12:18 am
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### Re: Autoprotolysis

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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