1.6 Amphoteric Substances
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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:
\(\ce{NH3(g) + H2O(l) <=> NH4^{+}(aq) + OH^{-}(aq)}\)
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:
\(\ce{HCl(g) + H2O(l) <=> H3O^{+}(aq) + Cl^{-}(aq)}\)
In this reaction, water is acting as a base because it accepts a proton from \(\ce{HCl(g)}\) .
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, \(\ce{HSO4-}\) acts as a base. In the second reaction it acts as an acid:
1. | \(\ce{HSO4^{-} + H3O^{+} <=> H2SO4 + H2O}\) | \(\ce{HSO4-}\) accepts a proton from \(\ce{H3O+}\) |
2. | \(\ce{HSO4^{-} + OH^{-} <=> H2O + SO4^{2-}}\) | \(\ce{HSO4-}\) gives (donates) a proton to \(\ce{OH-}\) |