Question

Please rank the following species in order of increasing basicity. Explain your reasons for ordering them as you do. Also please explain without giving pKa values but rather use ARIO explinations.

NH₃
CH₃O⁻
H₂O
CH₃COO⁻
NaOH
NH₂⁻
HSO₄⁻

Answer 1

The species are ranked from least to most basic using the ARIO principle: HSO4-, NH3, H2O, CH3COO-, CH3O-, NaOH, NH2-. This ranking is based on the stability of the negative charge, with resonance stabilization and atom electronegativity affecting basicity.

Step-by-step explanation:

To rank the given species in order of increasing basicity, we use the ARIO principle, which stands for Atom, Resonance, Induction, and Orbital, to assess the tendency of a species to donate an electron pair. Species with more electron density and less stable negative charges tend to be more basic. Here is the order from least basic to most basic:

1. HSO4−: Has a very stable negative charge due to resonance stabilization, so it's the least basic.
2. NH3: Is a neutral molecule with a moderate ability to donate an electron pair.
3. H2O: Slightly more basic than ammonia due to the oxygen atom being more electronegative than nitrogen, creating a greater electron density on the atom.
4. CH3COO−: The negative charge is delocalized by resonance, increasing its basicity compared to water.
5. CH3O−: Has a negative charge localized on oxygen; however, it doesn't have as much resonance stabilization as the acetate ion, making it more basic.
6. NaOH: The hydroxide ion (OH−) is a strong base due to its highly negative charge concentrated on the oxygen atom.
7. NH2−: As an anion with a single negative charge on a less electronegative atom than oxygen, ammonia is a very strong base.