Ka + Kb

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Chloe Alviz 1E
Posts: 102
Joined: Sat Aug 17, 2019 12:17 am

Ka + Kb

Postby Chloe Alviz 1E » Wed Jan 15, 2020 6:12 pm

During lecture, Dr. Lavelle mentioned how as Ka increases, Kb decreases. What is the reason for this?

Asha Agarwal 1E
Posts: 51
Joined: Fri Aug 30, 2019 12:16 am

Re: Ka + Kb

Postby Asha Agarwal 1E » Wed Jan 15, 2020 6:22 pm

Kw = Ka x Kb, so Ka and Kb are inversely proportional meaning as one increases the other decreases. This makes sense when thinking about the relative values of Ka and Kb for the strength of acids and bases as a strong acid will have a very high Ka resulting in a low Kb because it is not very basic and vice versa.

Daniel Toscano 1L
Posts: 95
Joined: Tue Nov 13, 2018 12:18 am

Re: Ka + Kb

Postby Daniel Toscano 1L » Wed Jan 15, 2020 6:31 pm

Another way to see it is that Ka+Kb=Kw, which is 14. If ka increases, then Kb must decrease in order to be equal to 14. If Kb increases, then Ka must decrease in order to be equal to 14.

Kristina Rizo 2K
Posts: 105
Joined: Wed Sep 18, 2019 12:19 am

Re: Ka + Kb

Postby Kristina Rizo 2K » Wed Jan 15, 2020 6:39 pm

This is irrelevant to the stated question, but does anyone know if we can still turn in chemical equilibrium hw questions for week 2? Or does it have to be acids and bases?

Kallista McCarty 1C
Posts: 212
Joined: Wed Sep 18, 2019 12:18 am

Re: Ka + Kb

Postby Kallista McCarty 1C » Wed Jan 15, 2020 8:22 pm

Kristina Rizo 2K wrote:This is irrelevant to the stated question, but does anyone know if we can still turn in chemical equilibrium hw questions for week 2? Or does it have to be acids and bases?

Since we still covered chemical equilibrium this week, you can turn in problems from that section as long as they are different than the ones you turned in last week!

Tyler Angtuaco 1G
Posts: 130
Joined: Wed Sep 11, 2019 12:16 am

Re: Ka + Kb

Postby Tyler Angtuaco 1G » Wed Jan 15, 2020 8:39 pm

This was in reference to the ionization constant for water, Kw, because the addition of both reactions in the example (the addition of water to ammonium and the addition of water to ammonia) resulted in the concentration of hydronium ions multiplied by the concentration of hydroxide ions (derived from Ka x Kb). Since Kw is a constant at a given temperature, the concentrations of hydronium and hydroxide are inversely proportional and as one increases, the other decreases.

Andrew Liang 1I
Posts: 105
Joined: Fri Aug 30, 2019 12:18 am

Re: Ka + Kb

Postby Andrew Liang 1I » Wed Jan 15, 2020 8:51 pm

Ka and Kb have an inverse proportional relationship. Ka x Kb = Kw. Kw is a constant therefore when Ka increases Kb must decrease in order to maintain the same constant value for Kw.


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