Using Ka vs Kb

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Connie Liang 3L
Posts: 59
Joined: Wed Sep 30, 2020 10:00 pm
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Using Ka vs Kb

Postby Connie Liang 3L » Sun Jan 17, 2021 12:40 am

If in one reaction you have an acid ionizing and a base gaining a proton at the same time, why would you use Ka over Kb and vice versa?

Hannah Biju 1E
Posts: 89
Joined: Wed Sep 30, 2020 9:55 pm

Re: Using Ka vs Kb

Postby Hannah Biju 1E » Sun Jan 17, 2021 1:11 am

If there is formation of an acid (H3O+), then you should use Ka. If there is formation of a base (OH-), then you should use Kb.

Muskaan Abdul-Sattar
Posts: 79
Joined: Wed Nov 13, 2019 12:19 am

Re: Using Ka vs Kb

Postby Muskaan Abdul-Sattar » Sun Jan 17, 2021 3:01 am

Hey! As Hannah said, I believe Ka is used when dealing with the formation of acids while Kb is used when dealing with the formation of bases.

Fiona Huang 3C
Posts: 36
Joined: Wed Nov 25, 2020 12:19 am

Re: Using Ka vs Kb

Postby Fiona Huang 3C » Sun Jan 17, 2021 4:02 am

If you have an acid dissociating or when H3O+ is formed, you would use Ka. When a base is dissociating, you would use Kb. Also, Ka x Kb = Kw = 10-14.

Julianna Shimabukuro 1D
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Re: Using Ka vs Kb

Postby Julianna Shimabukuro 1D » Sun Jan 17, 2021 4:17 am

As everyone else has stated, Ka is for the formation of acids and Kb is for the formation of bases. A way to memorize this is that Ka has an "a" in it for acids, and Kb has a "b" in it for bases.

Gicelle Rubin 1E
Posts: 81
Joined: Fri Oct 02, 2020 12:16 am

Re: Using Ka vs Kb

Postby Gicelle Rubin 1E » Sun Jan 17, 2021 4:21 am

Hannah Biju 1E wrote:If there is formation of an acid (H3O+), then you should use Ka. If there is formation of a base (OH-), then you should use Kb.


Thank you for your clarification! I had totally forgotten about this!

Rajshree 1F
Posts: 96
Joined: Wed Sep 30, 2020 9:32 pm

Re: Using Ka vs Kb

Postby Rajshree 1F » Sun Jan 17, 2021 9:05 am

if the product formed is H3O+ then Ka should be used and if OH- is formed then Kb should be used.

OmarArafat_2K
Posts: 36
Joined: Thu Dec 17, 2020 12:17 am

Re: Using Ka vs Kb

Postby OmarArafat_2K » Sun Jan 17, 2021 9:38 am

With Acid dissociations/formations, you use Ka. With base dissociations/formations, use Kb.

Sarah Huh 1K
Posts: 36
Joined: Wed Nov 18, 2020 12:26 am

Re: Using Ka vs Kb

Postby Sarah Huh 1K » Sun Jan 17, 2021 8:59 pm

Ka is used for the formation of acids (H30+ in product), while Kb is used for the formation of bases (OH-)


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