[khood]

What is the pK value for the following equilibria involving the neutralization of piperidine (C5H11N) with acid? (The Kb of piperidine is Kb = 1.3 x 10-3)
C5H11N + H3O+ <----> C5H11NH+ + H2O

Attempt at a solution: I solved for Ka by taking 1E-14/Kb
then I took -log(ka)
which I got to equal 2.89
this answer is wrong.. and I don't see how else to do the problem! any help would be GREATLY appreciated since i've been stuck on this problem for hours

[AWK]

Write down reactions for both equilibrium K_a and K_b. Your reaction is an inverse one for one of them

[khood]

Write down reactions for both equilibrium K_a and K_b. Your reaction is an inverse one for one of them

ohh okay so I found my Ka by taking Kw/Kb
then I inverted the Ka value
so now can i find the pK by taking the -log(1/Ka)
is this correct?

[AWK]

Calculate number!

[khood]

I got my answer to be -11.11
I've been inputing the number as 11.11
I'm assuming my only mistake was the lack of negative sign?

[Borek]

I'm assuming my only mistake was the lack of negative sign?

Most likely. That's what I was hinting at telling you (not here) that the equation you wrote was not for Ka.