In each of the following question, a statement of Assertion (A) is given followed by a corresponding statement of Reason (R). Choose the correct answer as:
Assertion (A): NF3 is a weak ligand than N(CH3)3.
Reason (R): NF3 ionizes to give F– ion in aqueous solution.
Answer & explanation
Correct answer: option 3
The correct answer is option 3. If the assertion is true, but the reason is false.
Let us break down the assertion and reason provided:
Assertion: \(NF_3\) is a weaker ligand than \(N(CH_3)_3\)
This assertion is true. In coordination chemistry, the term "ligand" refers to a molecule or ion that can donate a pair of electrons to form a coordinate bond with a central metal ion. The strength of a ligand is often determined by its ability to donate electron pairs effectively. In general, ligands with more available lone pairs tend to be stronger ligands. \(NF_3\) (nitrogen trifluoride) is considered a weaker ligand compared to \(N(CH_3)_3\) (trimethylamine) because nitrogen in NF3 has fewer available lone pairs for donation compared to nitrogen in \(N(CH_3)_3\).
Reason: \(NF_3\) ionizes to give \(F^–\) ion in aqueous solution
This reason is false. \(NF_3\) does not ionize to give fluoride ions \((F^–)\) in aqueous solution. Instead, \(NF_3\) acts as a Lewis base by donating a lone pair of electrons to form coordinate bonds with metal ions. The ionization behavior described in the reason does not apply to \(NF_3\).
In summary, while the assertion about \(NF_3\) being a weaker ligand than \(N(CH_3)_3\) is true, the reason provided to support it is false. \(NF_3\)'s weaker ligand strength is attributed to its lesser availability of lone pairs for donation compared to \(N(CH_3)_3\). Therefore, the correct answer is that the assertion is true, but the reason is false.