[Imo]

Why H+ react more with OH- than with F- ? H20 has more chance to be formed than HF.

Because F- is more electronegative?

[Babcock_Hall]

Which chemical species is the stronger base, OH^-1 or F^1-?

[zs3889]

Which chemical species is the stronger base, OH^-1 or F^1-?

The stronger the acid, the weaker its conjugate base. Is that how one would normally encounter this kind of question (to figure out which one is the stronger base)?

[Babcock_Hall]

Imo,

Which is the stronger acid HF (pKa = 3.5) or H2O (pKa = 15.7)?  Therefore (as zs3889 implies), which is the stronger base, hydroxide ion or fluoride ion?  Will H+ react with the stronger base or the weaker base?

[Imo]

Ah, thanks. But i have a new doubt now kk...why HCLO4 is more acid than HCLO ?the 3 oxygens would be let the H+ leaves easily, why?

[Babcock_Hall]

The question of why pKa values are what they are touched off a vigorous debate here a few weeks ago.  I will just offer my suggestion that the more oxygen atoms are present, the more spread out is the negative charge, making it more stable.  Others may disagree.

[ramboacid]

I hope I'm not restarting the aforementioned argument with this post, but I would also like to put in my own two cents here and say that, in addition to stabilizing the conjugate base, the extra highly electronegative oxygens withdraw electron density from the acidic O-H bond, thus making it weaker and more likely to ionize the hydrogen.

@Babcock_Hall: Do you have the link to that thread? I feel that it would make a very interesting and enlightening read, as I wasn't aware that they was so much discrepancy on the issue.

[Babcock_Hall]

I think that this was it:  http://www.chemicalforums.com/index.php?topic=55865.0

[ramboacid]

Thanks for the link! I guess there is a lot more to acid-base chemistry than I thought

[orgopete]

I am not wishing to repeat the acidity arguments here. I was simply suggesting that if one were to try to explain why hydrogen atoms may be removed to form a conjugate base, that one should create a general model for acidity. Why should perchloric acid have a different rationale for ionization than HBr? I was arguing or asking, "How are the electrons of HBr different than those of perchloric acid?" Although it is expedient to argue as Babcock_Hall has,

…my suggestion that the more oxygen atoms are present, the more spread out is the negative charge, making it more stable. 

I found it difficult to rationalize how resonance participation should to lead to an increase in acidity. My focus was on the H-X bond. I could understand that if electrons were pulled toward the X-atom, they would be pulled away from the proton and acidity should increase. I would argue this is the kind of effect one should find for a comparison of HOH and HOCl. Replacing a proton with a chlorine should pull electrons away from the oxygen and the O-H bond. Doing so, increases the proton-electron pair distance and acidity.

It could be possible to pull electrons away in a hyperconjugation way. Therefore I suggested pyrrole. In pyrrole, the electrons of the nitrogen are part of the aromatic ring by resonance. The NH acidity is still much higher than an isolated amine. Deprotonation of pyrrole left the N-H electrons attached to the nitrogen, but orthogonal to the pi electrons that are part of the aromatic ring. I was arguing that an increase in acidity was not a resonance effect, but rather an inductive effect, that is just as replacing a proton with a chlorine increased the acidity of HOCl.

I think I received about ten flags for this, so this idea was not popular.