Chemistry · Coordination Compounds

JEE Main 2025 — 24 January, Morning Shift — Question 28

One mole of the octahedral complex compound $\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}_{3}$ gives 3 moles of ions on dissolution in water. One mole of the same complex reacts with excess of $\mathrm{AgNO}_{3}$ solution to yield two moles of $\mathrm{AgCl}_{(\mathrm{s})}$ . The structure of the complex is :

Option A:
$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{Cl}_{2}$
Correct
Option B:
$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}\right] \cdot \mathrm{Cl}_{2} \cdot \mathrm{NH}_{3}$
Option C:
$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl} \cdot \mathrm{NH}_{3}$
Option D:
$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right] .2 \mathrm{NH}_{3}$

Answer: A

Step-by-step solution

$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{Cl}_{2} \rightarrow \underbrace{\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right]^{2+}(\text { aq. })+2 \mathrm{Cl}^{-} \text {(aq.) }}_{3 \text { ions in water }}$

$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \mathrm{Cl}_{2}$ (aq.) $+2 \mathrm{AgNO}_{3}$ (aq.) $\rightarrow$

$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right]\left(\mathrm{NO}_{3}\right)_{2}$ (aq.) $+2 \mathrm{AgCl}(\mathrm{s})$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 24 January, Morning Shift
Subject: Chemistry
Chapter: Coordination Compounds
Topic: Isomerism in Coordination Compounds