Organic Chem Acidity/Bascity

[Wow Strong Armz]

all right, for the life of me i can't diffrentiate between what is a strong acid/ weak acid. strong base/weak base. Say they give you HCN how do u know if that is a weak acid or strong? Thanks

 

[ForcedEntry]

Strong v. weak is a relative concept. When comparing two organic compounds...Dr. Musgrave had a shirt that said, "Acidity is dependent upon the resulting anion's stability". It works everytime.

Also, just follow the simple O v. H rule from Chem I.

 

[binghamkid]

There's only a few strong acids and a few strong bases that will be tested (as long as they aren't testing your concept of pKa values). Just memorize them if you have trouble.

6 strong acids you have to remember are
HCl, HBr, HI, H2SO4, HNO3, HClO4.

Any strong base is one with an alkali or alkali-earth metal with an OH group attached to it.

 

[Wow Strong Armz]

and in order of acidity would this be correct?

H2SO4, HNO3, HClO4 HCl, HBr, HI,

 

[Bhavesh]

and in order of acidity would this be correct?

H2SO4, HNO3, HClO4 HCl, HBr, HI,

I agree with what bingham said: there are only so many you have to know, and you should memorize what they are so you recognize them

An additional explanation I found in a book is:
-oxyacids: the more oxygens present, the stronger the acid
-polyprotic acids: the more hydrogen bonds of oxygen lost hydronium ions, the strong the acid
Thus, the acid with the most oxygen and the lowest charge is the strongest.

That explanation helps when you have to choose between compounds such as H2SO4 and H2SO3.

I'm not sure that explanation really helps to answer your question, but based on the pKa's on wikipedia:

HI>HBr>HCl>H2SO4>HN03

The pKa's are so close, that I'm not sure on the PCAT they'd ask which one is stronger.