Hey guys, in this new video, we're going to take a look at amphoteric species. We've been floating around this idea. We've been saying for example that water is an example of an amphoteric species. It can act as an acid in some equations, but as a base in another. That's the whole idea of amphoteric species. They act as acids and as bases. Here we’re going to say an amphoteric species or an amphiprotic species is a compound that can act as an acid or as a base. Water is the great example. Water can give away an H to become OH-. Here it's acting as an acid. It gives away an H to something to create this conjugate base. Or water could act as a base itself. It can accept an H positive to become H3O+. In this case, this would be the conjugate acid.
Now we're going to say here, partially dissociated conjugate bases a polyprotic acids are also amphoteric. What the heck does that mean? Basically it means, we say that polyprotic acids are acids with more than one H+. Example: H2SO4, H3PO4, H2CO3. These are all polyprotic. They have more than one H+ in their formula. We’re saying the partially dissolved forms of them. That means when you take off their first H, here we’re going to get HSO4 minus, H2PO4 minus, HCO3 minus. This one can actually break down one more to give us an amphoteric species. Those are our examples.
Here we’re going to say, these compounds, these amphoteric species have something in common. They all possess and H+. All of them possess an H, at least one H. All of them posses a negative charge. All of them have a negative charge. We’re going to say if you have an H in the front and you have a negative charge in the back or end of the compound, that species can act as an amphoteric species. Water of course is an exception to that because water doesn't have a negative charge on it. But it does have H’s so it could still be amphoteric. That's all we can say here.
Now we're going to say based on this definition, I want you guys to answer these following questions. It says: Which of the following species is/are amphoteric? Go to the definition of what an amphoteric or amphiprotic species is in order to answer this. Look to see is only one amphoteric species or is there more than one. Good luck!
Practice: Which of the following species is/are amphoteric?