Identify the Lewis acid and Lewis base among the reactants in each equation. a. Fe3+(aq) + 6 H2O(l)Fe(H2O)6 3+(aq) b. Zn2+(aq) + 4 NH3(aq)Zn(NH3)4 2+(aq) c. (CH3)3N(g) + BF3(g)(CH3)3NBF3(s)

Understanding Lewis acids is crucial when studying chemical reactions, particularly those involving the transfer of electron pairs. A Lewis acid is defined as any species that can accept an electron pair. This is slightly different from the classical definition of an acid by Arrhenius or Brønsted-Lowry, which are based on hydrogen ions or proton transfer respectively. In the exercises given, the Lewis acids identified are Fe3+ and Zn2+, both metal ions with empty orbitals ready to accept electrons, as well as the molecule BF3 with an empty p orbital in its boron atom.

Characteristics of Lewis acids include the presence of vacant orbitals that can accommodate electron pairs, being able to pull or attract electrons towards themselves, and often being found in the form of positive ions or neutral molecules with electron-deficient atoms.

Conversely, a Lewis base is identified as a species that donates an electron pair. In the reactions presented in the exercise, the Lewis bases are H2O, NH3 (ammonia), and (CH3)3N (trimethylamine). These molecules have lone pairs of electrons that are not involved in bonding and are, hence, available to be shared with other atoms or ions.

Common Properties of Lewis Bases:

• Have at least one lone pair of electrons.
• Often contain heteroatoms like nitrogen, oxygen, or sulfur that have lone pairs.
• Can form coordinate covalent bonds by donating their electron pair.

Lewis bases can vary greatly in strength based on their ability to donate electrons, which is influenced by the electronegativity and the size of the atom with the lone pair.

Electron pair donation is the hallmark of a Lewis base, as seen in the textbook exercises. Molecules or ions like H2O and NH3 participate in chemical reactions by offering their lone pairs to other species that lack electrons, resulting in new chemical bonds. The ease with which a Lewis base donates its electrons depends on several factors, including the stability of the resulting compound and the electronegativity difference between the donor atom and the acceptor atom. In the exercises, NH3 donates a lone pair of electrons to the Zn2+, and H2O donates to Fe3+, demonstrating the principle of electron pair donation in forming complex ions.

Complexation reactions are a subset of chemical reactions where a complex is formed by the Lewis acid-base interaction. The Lewis base with its free electron pair forms a coordinate bond with the Lewis acid, which has an empty orbital. The result of this interaction is a complex ion or compound, where the base is typically referred to as the ligand, and the acid is the central ion or atom. Such reactions are not only fundamental in understanding chemical bonding but are also crucial in various industries, from pharmaceuticals to materials science. The reactions in the exercises, involving the formation of Fe(H2O)6 3+ and Zn(NH3)4 2+, are classic examples of complexation reactions, illustrating the central role played by electron pair donation in the creation of new substances.