Q42 · CSIR NET Chemistry, June 2019
Paper: CSIR NET June 2019 · Subject: Inorganic Chemistry · Chapter: Coordination Chemistry · Topic: Reaction Mechanisms Substitution · Marks: 2 · Difficulty: Medium
The products A and B for the given reaction
\[ \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right]^{2+}+\left[\mathrm{Cr}\left(\mathrm{OH}_{2}\right)_{6}\right]^{2+}+5 \mathrm{H}_{3} \mathrm{O}^{+} \rightarrow \mathrm{A}+\mathrm{B} \]
are respectively,(a)$\left[\mathrm{Co}\left(\mathrm{OH}_{2}\right)_{5} \mathrm{Cl}\right]^{+},\left[\mathrm{Cr}\left(\mathrm{OH}_{2}\right)_{6}\right]^{3+}$
(b)$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{OH}_{2}\right)\right]^{2+},\left[\mathrm{Cr}\left(\mathrm{OH}_{2}\right)_{5} \mathrm{Cl}\right]^{2+}$
(c)$\left[\mathrm{Co}\left(\mathrm{OH}_{2}\right)_{6}\right]^{2+},\left[\mathrm{Cr}\left(\mathrm{OH}_{2}\right)_{5} \mathrm{Cl}\right]^{2+}$
(d)$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right]^{+},\left[\mathrm{Cr}\left(\mathrm{OH}_{2}\right)_{6}\right]^{3+}$
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
Inner-sphere reduction transfers the chloride: Cr(II) becomes [Cr(H₂O)₅Cl]²⁺, and the labile Co(II) product loses its NH₃ to the acid, giving [Co(H₂O)₆]²⁺.
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