1.6 Amphoteric Substances
Were you surprised in the last section to see water being described as an acid? In the ammonia reaction, water acted as an acid because it donated a proton (hydrogen ion) to ammonia:
NH3 (g) + H2O(l) ↔ NH4+(aq) + OH–(aq)
Compare this to another reaction we looked at earlier when we saw how hydrochloric acid acted as an acid by donating a proton to water:
HCl(g) + H2O(l) → H3O+(aq) + Cl-(aq)
In this reaction, water is acting as a base because it accepts a proton from HCl.
Substances that can act as Just to confuse you, the term |
Here is another example of an amphoteric substance. In the first reaction the bisulfate ion, HSO4– acts as a base. In the second reaction it acts as an acid:
|
1.
|
HSO4– + H3O+ ↔ H2SO4 + H2O | HSO4– accepts
a proton from H3O+ |
|
2.
|
HSO4– + OH– ↔ H2O + SO42- | HSO4– gives (donates)
a proton to OH – |
Time to do some practice exercises, followed by Assignment 1.
