 So now we're going to talk about the classifications of acid. We can break acids up into two groups. There's the mono-protic and the polyprotic. Mono means one, protic means proton, so one proton. Poly means many, protic again means proton, so many protons. So mono-protic acid donates only one proton whereas polyprotic acids can donate two or more protons. We further break up the polyprotic acids into dye and tri-protic, so we'll look at that on the next slide. So let's have a look at the mono-protic acids to start with. Then we'll look at the polyprotic acids down here. If we have a look at this nitric acid molecule here, we can tell it's nitric acid. It's got a nitrogen there, three oxygens and a hydrogen, so HNO3. The reason why it's an acid is because this hydrogen atom here breaks off and that produces the proton. Now remember, acids are proton donors. Now, nitric acid only has this one hydrogen here that it can donate. That's why it's a mono-protic acid, it's only donating one hydrogen. If we look at a cetic acid over here, ethanoic acid, so CH3C00H, the hydrogen that breaks off is this one here. Not these ones attached to the carbon, they're attached fairly strongly. It's this oxygen-hydrogen bond where this hydrogen can break off. So again, this is mono-protic, this hydrogen here is the one that breaks off. Now, the polyprotic acids, like I said, there's di-protic, tri-protic, and theoretically, you could have tetraprotic, which is we've got four protons that can break off. There you're looking for two unstable hydrogens that can break off. So here we've got sulfuric acid. So we've got these two OHs attached to the sulfur, and then we've got double bonds between the sulfur and these two oxygens. What happens is this hydrogen and this hydrogen, again, we've got that unstable bond between the oxygen and the hydrogen, they're the hydrogens that can break off. When that happens, you get a sulfate ion left over SO4 2 minus. So because it can donate two protons, that makes it di-protic, di-means two. If we look at tartaric acid over here, we can see we've got two carboxylic acid groups at the end of the chain, and we've got two hydroxyl groups over here. Now, for these ones, the hydrogens aren't breaking off of the hydroxyl groups here, they're breaking off of the carboxylic acid groups, and that's why they're an acid, it's carboxylic acid. So the hydrogens break off of the carboxylic acid part. Again, we've got two there, so it can donate two. If you look at tri-protic acid, so tri-means three, so they can donate three protons. So let's have a look at an example, we've got citric acid over here. So citric acid is a tri-carboxylic acid, there's three carboxylic acid groups there. So this hydrogen, this hydrogen, this hydrogen, those three break off, and that makes it tri-protic.