[osker246]

Problem:

Calculate the pH for each of the following:

a) 0.10 M aniline (C6H5NH2) solution (Kb=4.3x10^-10

b)0.10 M C6H5NH3Cl solution (Kb=4.3x10^-10

Attempt:

Well I'm having a hard time figuring out which both of those substances dissociate too. Part A I think I have worked out properly I think it goes something like this.

C6H5NH2 + H2O <====> C6H5NH3⁺ + OH^-

I set up a ice chart showing that [OH^-]=6.6x10-6, which pH=8.82

Now for part B im having a hard time seeing what the dissociation reaction looks like. Is this is it?

C6H5NH3Cl + H2O <====> C6H5NH3ClH⁺ +OH^-

I'm having a hard time figuring out what the conjuage base or acid to this would be. If anybody can help I would appreciate it. Thank you!

[AWK]

C₆H₅NH₃⁺ + H₂O <====> C₆H₅NH₂ + H₃O⁺

[osker246]

So C₆H₅NH₂ is the conjugate acid correct? I would need solve for Ka and then set up an ICE chart to solve for [H_3O⁺]?

[AWK]

aprox.
[H₃O⁺]= SQRT(K_a x [NH₄⁺])

note: K_a concerns anilinium cation

[Borek]

So C₆H₅NH₂ is the conjugate acid correct?

No, it is a conjugate base. You have a reaction

RH⁺ <-> R + H⁺

RH⁺ is an acid, R is a conjugate base.