Question

The correct statement(s) about the ligand substitution/exchange reaction is/are

• A. he rate is faster in the case of SF₆ than in [AlF⁶]³⁻ .
• B. The rate is faster in the case of [Mg(H2O)₆]²⁺ than in [Sr(H₂O)₆]²⁺
• C. The rate of water exchange is faster in the case of [Ni(H₂O)₆] ²⁺ than in [Co(NH₃)₅(H2O)]³⁺
• D. The rate is faster in case of [Cr(H₂O)₆] ²⁺ than in [Cr(H₂O)6] ³⁺

Answer 1

The Correct Option is C, D

• (A) The rate is not necessarily faster in the case of SF₆ than in [AlF₆]³⁻, because the size and charge of the metal ion as well as the nature of the ligands play a significant role in the rate of substitution reactions.
• (B) The rate of substitution reactions generally increases as the size of the metal ion increases, meaning [Mg(H₂O)₆]²⁺ will have a slower rate than [Sr(H₂O)₆]²⁺, not the other way around.
• (C) The rate of water exchange is faster in [Ni(H₂O)₆]²⁺ compared to [Co(NH₃)₅(H₂O)]²⁺ due to the difference in the coordination environment and the charge distribution around the central metal ion.
• (D) The rate of substitution is generally faster in [Cr(H₂O)₆]²⁺ than in [Cr(H₂O)₆]³⁺, because the higher charge on the chromium ion in [Cr(H₂O)₆]³⁺ results in stronger ligand binding and slower exchange.

Thus, the correct answers are (C) and (D).