Chemistry · Coordination Compounds

JEE Main 2025 — 24 January, Evening Shift — Question 33

When Ethane-1,2-diamine is added progressively to an aqueous solution of Nickel (II) chloride, the sequence of colour change observed will be :

Option A:
Pale Blue $\rightarrow$ Blue $\rightarrow$ Green $\rightarrow$ Violet
Option B:
Pale Blue $\rightarrow$ Blue $\rightarrow$ Violet $\rightarrow$ Green
Option C:
Green $\rightarrow$ Pale Blue $\rightarrow$ Blue $\rightarrow$ Violet
Correct
Option D:
Violet $\rightarrow$ Blue $\rightarrow$ Pale Blue $\rightarrow$ Green

Answer: C

Step-by-step solution

$\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]_{(\mathrm{aq})}^{+2}+\mathrm{en}_{(\mathrm{aq})} \rightarrow\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}(\mathrm{en})\right]_{(\mathrm{aq})}^{+2}+2 \mathrm{H}_{2} \mathrm{O}$ Green

$\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}(\mathrm{en})\right]_{(\mathrm{aq})}^{+2}+\mathrm{en}_{(\mathrm{aq})} \rightarrow\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{en})_{2}\right]_{(\mathrm{aq})}^{+2}+2 \mathrm{H}_{2} \mathrm{O}$ Pale Blue

$\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{en})\right]_{(\mathrm{aq})}^{+2}+\mathrm{en}_{(\text {aq) }} \rightarrow\left[\mathrm{Ni}(\mathrm{en})_{3}\right]_{(\text {aq) }}^{+2}+2 \mathrm{H}_{2} \mathrm{O}$ Blue / purple

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

The conditions and consequence that favours the t 2 g ^3, e g ^1 configuration in a metal complex are :

Answer: C

Step-by-step solution

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