Weak Acids...memorize or not for the test?

[kevo246]

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So I have the strong acids understood, and the strong bases as well, but is it a good idea to memorize the weak acids as well? Would it be logical to just state that anything other than the strong acid is considered weak?

 

[Etorphine]

No, yes.

 

[apumic]

So I have the strong acids understood, and the strong bases as well, but is it a good idea to memorize the weak acids as well? Would it be logical to just state that anything other than the strong acid is considered weak?

Dude.... yes, memorize the weak acids. Oh, and good luck w/ that!


Really, don't memorize the strong ones either. You must know why they're strong! The MCAT's not going to ask you if H2SO4 is a strong acid. It's going to ask which acid/base titration curve w/ LDA is sulfuric and which is chromic acid based solely upon the shape (i.e., no numbers given). It's all about application. Memorization is one of the biggest wastes of time you could commit when studying for the MCAT. (To solve that problem you first know the relevant chemical formulas, then you need to be able to look at the differences between H2SO4 and H2CrO4 and determine acidity trends. Finally, you need to put that together to come up with the difference in the titration curve.)

 

[kevo246]

OK, so I should feel good then. I completely understand why a strong acid is a STRONG acid, the stability of the conjugate BASE. Therefore I would be able to predict a strong acid from its resonance structure. Now how about predicting its acidity compared to a weaker acid? Is there a threshold of stability that makes an acid unable to completely dissociate?

Thanks for the reality check btw with applications.....I need that sometimes after studying for long intervals!

 

[apumic]

OK, so I should feel good then. I completely understand why a strong acid is a STRONG acid, the stability of the conjugate BASE. Therefore I would be able to predict a strong acid from its resonance structure. Now how about predicting its acidity compared to a weaker acid? Is there a threshold of stability that makes an acid unable to completely dissociate?

Thanks for the reality check btw with applications.....I need that sometimes after studying for long intervals!

Yes... the solvent. For H2O, that means OH- or stronger --> strong base; H3O+ or stronger --> strong acid. The definition is simply that the acid disassociates completely in the solvent (i.e., it is at least as strong an acid as the conjugate acid of thesolvent). It's the reverse for the base.