Kw

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Helen Mejia 1I
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Joined: Fri Sep 28, 2018 12:24 am

Kw

Postby Helen Mejia 1I » Tue Jan 15, 2019 8:36 pm

Can someone please explain why the concentration of H3O+ equals the concentration of OH-?
I am referring to question 6A.21. This question is asking what is the concentration of H3O+ ions at 37 C. Kw= 2.1 x 10^-14

ThomasLai1D
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

Re: Kw

Postby ThomasLai1D » Tue Jan 15, 2019 9:36 pm

Because the conversion of H2O,in pure water, into H3O+ and OH- is an autoprolytic reaction, this necessitates that the concentrations of OH- and H3O remain the same. In other words, for H3O+ to be formed, a proton must dissociate from an H2O molecule and bind to another H2O molecule, thus creating OH- (in the former H2O molecule) and H3O+ (in the latter).

Shreya_Bharadwaj_1D
Posts: 38
Joined: Fri Sep 28, 2018 12:22 am

Re: Kw

Postby Shreya_Bharadwaj_1D » Wed Jan 16, 2019 1:16 am

Kw refers to the concentration of water molecules and since water is a neutral substance on the pH scale, the concentrations of [H3O+] and [OH-] are the same because when you calculate the pH given these numbers, you will get 7, which is right in the middle of the pH scale

Danny Elias Dis 1E
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Joined: Fri Sep 28, 2018 12:19 am

Re: Kw

Postby Danny Elias Dis 1E » Wed Jan 16, 2019 10:05 am

Also, you must keep in mind that we do not begin with any H3O+ or OH- in the solution. It starts out as 100% H2O. After that, as previously stated, note that H3O+ cannot be created without the formation of OH- in a pure water solution.

Helen Mejia 1I
Posts: 67
Joined: Fri Sep 28, 2018 12:24 am

Re: Kw

Postby Helen Mejia 1I » Sun Jan 20, 2019 7:34 pm

Thank you!


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