Applying Kw

Moderators: Chem_Mod, Chem_Admin

Posts: 127
Joined: Fri Aug 30, 2019 12:15 am
Been upvoted: 1 time

Applying Kw

Postby KDang_1D » Sun Jan 19, 2020 10:59 pm

In lecture, Dr. Lavelle did an example using Ba(OH)2 to show that Kw, a special value of Ka, can be used to determine [H3O+]. Why is this possible? Don't all aqueous reactions have different Ka values, so shouldn't Ba2+ affect the value of Ka/Kw?

Posts: 109
Joined: Sat Sep 07, 2019 12:17 am
Been upvoted: 1 time

Re: Applying Kw

Postby sbeall_1C » Sun Jan 19, 2020 11:18 pm

Ba2+ is the cation of a strong base, so when it dissociates it will not affect the pH of the solution. Kw refers to the equilibrium constant for water, and shows how water has a neutral pH of 7. So the OH will increase the pH which changes the Kb and therefore allows us to calculate the Ka using Kw=(Ka)(Kb)=1.0x10^-14.

Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

Re: Applying Kw

Postby Jared_Yuge » Sun Jan 19, 2020 11:25 pm

Kw is really nifty because if you have one of [OH-] or [H30+] you can find the other because you know Kw is 10^-14. Ba(OH)2 adds to the [OH] (you know Ba2+ doesnt affect) then you use the new [OH-] to find the [H30+].

Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 4 guests