Why does NH3 favor the formation of [Cu(NH3)4]2+ over H2O?

Why does NH3 favor the formation of [Cu(NH3)4]2+ over H2O?

• A. NH3 is less electronegative than H2O
• B. NH3 is a stronger Lewis base
• C. NH3 has higher ionization energy
• D. NH3 forms covalent bonds more easily

Answer: (B)

The formation of the complex ion [Cu(NH3)4]2+ over water occurs primarily because ammonia (NH3) acts as a stronger Lewis base compared to water (H2O). A Lewis base is defined as a species that donates an electron pair to form a bond with a Lewis acid. In this case, copper(II) ions (Cu2+) can accept electron pairs from ligands to form a complex. Ammonia has a lone pair of electrons on the nitrogen atom, which allows it to effectively donate its electron pair to the Cu2+ ion. This strong donation capability enhances the stability of the resulting complex, promoting the formation of [Cu(NH3)4]2+. In contrast, water, while it can also act as a Lewis base (through the oxygen atom), is generally a weaker donor due to its greater polarization and higher electronegativity than nitrogen in ammonia. This makes NH3 more favorable for complexation with transition metals like Cu2+, leading to the formation of the ammonia complex rather than with water. Other options do not accurately capture the primary reason for preferential complex formation; for example, while NH3 is less electronegative than H2O, this does not directly correlate

The formation of the complex ion [Cu(NH3)4]2+ over water occurs primarily because ammonia (NH3) acts as a stronger Lewis base compared to water (H2O). A Lewis base is defined as a species that donates an electron pair to form a bond with a Lewis acid. In this case, copper(II) ions (Cu2+) can accept electron pairs from ligands to form a complex.

Ammonia has a lone pair of electrons on the nitrogen atom, which allows it to effectively donate its electron pair to the Cu2+ ion. This strong donation capability enhances the stability of the resulting complex, promoting the formation of [Cu(NH3)4]2+.

In contrast, water, while it can also act as a Lewis base (through the oxygen atom), is generally a weaker donor due to its greater polarization and higher electronegativity than nitrogen in ammonia. This makes NH3 more favorable for complexation with transition metals like Cu2+, leading to the formation of the ammonia complex rather than with water.

Other options do not accurately capture the primary reason for preferential complex formation; for example, while NH3 is less electronegative than H2O, this does not directly correlate