[Hello12]

I don't understand how you determine whether an acid is Monoprotic or DiProtic? ive checked the internet but i still dont understand.

[Arkcon]

I normally hate to say, use a common English dictionary, to tackle a chemical concept.  But in this case, I think it would be a good way to learn.  You have the common latin prefixes mono- and di-, and you should know what they mean.  Now then, -protic, can you make a guess?  Can you find an example of a monoprotic and diprotic acid, and can you see the difference?  Would a triprotic acid make it more obvious?

[Arkcon]

Oh, and try to search harder, a quick Google leads me to Wikipedia, which does mention the concept.  It is likely on the first page of the relevant chapter in your textbook as well.

[Hello12]

ok so HCL is Monoprotic, H2S04 is diProtic. and they are like this because they are able to donate 1 or 2 proton's per acid molecule. But how do i work out whether they are Monoprotic, diprotic for example what would Butyric acid (C4H8O2) be?

[Arkcon]

OK, now the organic acids are a little tricky for the newbs.  You're either told by the teacher, or you read it's description somewhere and memorize -- or, you take two years of university Basic Chem, and two years of Organic Chem -- all to learn one tiny fact: 

there is a functional group in organic chemistry nomenclature called the carboxyl group.  A carbon atom, double bonded to an oxygen atom, bonded to another oxygen, which is bonded to a hydrogen -- will donate that hydrogen, and only that hydrogen*, in aqueous reactions we normally associate with the term acid, according to the Arrhenius** definition of acid.

You will be able to tell by the structure, if you draw it out, insead of just listing the atoms, can you do that for butyric acid?.  For example, triprotic acids are very important in biochemical pathways, can you find some examples?

*Disclaimer: under various conditions, other organic compounds may donate a proton, see any common organic chem text for more specificity.

**Disclaimer: there are multiple definitions of the term "acid", see college level chem text for more specifics.

[Arkcon]

Ummm ... I re-read, and notice I didn't describe a carboxyl group well at all.  See this image ripped from wikipedia:



Well, that doesn't work. Try this:

http://en.wikipedia.org/wiki/Image:Carboxylic-acid.svg

[Hello12]

Thanks for the link and the explaination it helped alot