Amphoteric

[Ziyi Meng 2K]

Hi,

How do you know if a compound is amphoteric? Or that it can act as a Bronsted acid or base?

Also, could someone help explain to me what it means that an acid is a proton donor? I didn't really understand the donating proton part.

Thanks.

[Preston Pham 2H]

An amphoteric has properties of both a base and an acid. So this means that they remove hydrogen ions from an acid or add hydrogen ions on a base. This basically means that it can be a bronsted acid/base. An acid is a proton donor because when you see acids they usually have an H+ with them like HCL or HBr or HI. Strong acids tend to dissociate more and thus are more likely to give up these protons or in otherwords (H+) to the base.

[Anna Guan]

An acid is a proton donor because in water/solution, the compound will dissociate into H+ (proton), and the other part of it. That H+ is probably going to combine with the solution, therefore making the acid a proton donor.

[Hayden Jackson]

In terms of determining if a substance is amphoteric, you should look at the oxygens and hydroxides on the molecule and if say an oxygen has only 1 bond and therefore an oxidation number of -1, it can accept a proton and and act as a base, but if it other spots it has hydrogens it can give, that could be one way to tell. I am also a bit confused by it. In terms of acids being proton donors, H+ is the proton since hydrogen is only made of one proton and one electron, and since the electron is gone, H+ is just a proton, which is why compounds like HCl and HBr are acids because they separate into H+ and Cl- for example in water, and that H+ is "given" or "donated" to the H2O molecule which turns it into H3O+. Hope this helps!

[Ryan M]

Adding on to all the other replies, water is the main example to know- the acids and bases h it went over how it can act as both! I don’t think there will be too many cases where we will have to identify random compounds as amphoteric, but the concept is good to know.

[Kimia Rategh 2A]

Hi! So something is amphoteric if it acts as both a base and an acid. If we consider the Bronsted-Lowry definition of acids and bases, we know that an acid is a proton donor meaning that it gets rid of one of its protons which is then picked up by another compound, often a base. Therefore, a base is a proton acceptor meaning that it takes on a proton, sometimes one that is given off by an acid. Thus, if something is amphoteric it means that it can both receive or donate a proton. Water is the best example of this where in reactions with a base, it acts as an acid and gives away one of its protons resulting in the production of a conjugate acid and OH-. Similarly, if water reacts with an acid, it acts as a base and accepts the proton that the acid donates resulting in a conjugate base and H3O+. Hope this helps!

[Om Patel]

an amphoteric compound is one that has properties of both an acid and a base. it can have a negative sign and a H+ proton in the compound giving it properties of both

[Aida Fraser 2I]

are metalloids always amphoteric?

[Sarah Wang 1I]

A good rule of thumb is that metalloid oxides are amphoteric.