Question Bank › Inorganic Chemistry › Coordination Chemistry › ABC26IN0399The rate of the following redox reaction is slowest when X is [CoIII (NH₃)₅ X]3+/ 2++ [CrII (H₂ O)₆]²⁺ →… · ABC26IN0399 Subject: Inorganic Chemistry · Chapter: Coordination Chemistry · Topic: Coordination – General · Exam: GATE 2005-2021 · Marks: 2 · Difficulty: Medium
The rate of the following redox reaction is slowest when X is \[ \left[\mathrm{Co}^{\text {III }}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{X}\right]^{3+/ 2+}+\left[\mathrm{Cr}^{\text {II }}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+} \rightarrow\left[\mathrm{Co}^{\text {II }}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{H}_{2} \mathrm{O}\right)\right]^{2+}+\left[\mathrm{Cr}^{\text {III }}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{X}\right]^{3+/ 2+} \]
(a) $\mathrm{H}_{2} \mathrm{O}$
(b) $\mathrm{NH}_{3}$
(c) $\mathrm{Cl}^{-}$
(d) $\mathrm{N}_{3}{ }^{-}$
Answer Answer: B ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation The Cr(II) reduction goes fastest by the inner-sphere route through a bridging X (N₃⁻, Cl⁻ excellent; H₂O poor but possible). NH₃ has no spare lone pair and cannot bridge at all, so the reaction is slowest for X = NH₃.
← Previous in chapter · Chapter list · Next in chapter → Study loop for Coordination Chemistry
Open in whiteboard · Browse this chapter in the app