[Nescafe]

Hi,

Does the pka of the conjugated acid of X = pkb of X?

Also, the lower the Pkb, the stronger the base, according to this it means aniline is a stronger base than ammonia, is it really? According to the chart in the website below the pkb of ammonia is 9.25 whereas that of aniline is 4.63. I am so confused right now :S


http://www.sanderkok.com/techniques/laboratory/pka_pkb.html

Nescafe.

[Rutherford]

That is surely a mistake. They gave the value of its conjugated acid pK_a.
pK_a of conjugated acid is calculated by the following formula: pK_w=pK_a+pK_b. From here you can calculate that the pK_b of ammonia is around 4.75.
And for aniline they gave the pK_a of the conjugated acid. Now, you calculate the pK_b  .

[Nescafe]

That is surely a mistake. They gave the value of its conjugated acid pK_a.
pK_a of conjugated acid is calculated by the following formula: pK_w=pK_a+pK_b. From here you can calculate that the pK_b of ammonia is around 4.75.
And for aniline they gave the pK_a of the conjugated acid. Now, you calculate the pK_b  .

Thanks for the response. It is my mistake of putting too much faith into websites to a point that I question my understanding of the whole subject! Alright, I am good =) Thanks!

Nescafe.

[Borek]

Compare http://www.chembuddy.com/?left=pH-calculation&right=bronsted-lowry-theory

There is something wrong with the link you posted - at least I am getting 404 when trying to see the page.