To understand why the amide ion (NH2–) is a much stronger base than the hydroxide ion (OH–), we need to look at their structures and how they interact with protons (H+).
The amide ion is derived from ammonia (NH3), and it has a lone pair on the nitrogen atom that readily donates to protons, making it very basic. In contrast, the hydroxide ion also has a lone pair, but it is less able to stabilize an additional proton due to the negative charge on the oxygen atom. This makes NH2– a stronger base than OH–.
Now, when comparing the acids, NH3 and H2O, we need to consider their ability to donate protons. Water is a very stable molecule and can easily donate a proton to become hydroxide (OH–), which signifies its acidic character. On the other hand, ammonia can accept a proton to become ammonium (NH4+), but it is less likely to donate a proton compared to water.
In terms of acidity, H2O is a stronger acid than NH3 because it has a higher tendency to lose a proton and form OH–.
In summary, the amide ion (NH2–) is a stronger base than the hydroxide ion (OH–), while water (H2O) is the stronger acid compared to ammonia (NH3).