Ka and Kb values

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Julia Lung 1I
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Joined: Fri Jun 23, 2017 11:39 am

Ka and Kb values

Postby Julia Lung 1I » Thu Jan 24, 2019 10:42 am

I'm confused on how to select the correct Ka and Kb value from the table given in the textbook when they are not exactly what's in the problem. For example, in 12.71 to calculate the pH of 0.63M of NaCH3CO2(aq) would I just use the Ka value for acetic acid CH3COOH (1.8x10^-5)?

Eshwar Venkat 1F
Posts: 32
Joined: Fri Sep 28, 2018 12:22 am

Re: Ka and Kb values

Postby Eshwar Venkat 1F » Thu Jan 24, 2019 12:02 pm

Since you are given an initial concentration value of NaC2H3O2, which dissociates into Na+ and C2H3O2-, you need to write out a reaction where the acetate ion reacts with water to form acetic acid and the hydroxide ion. This means that you need to use Kb to find the pOH and then convert to the pH.

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