When Ethane-1,2-diamine is added progressively to an aqueous solution of Nickel (II) chloride, the sequence…

When Ethane-1,2-diamine is added progressively to an aqueous solution of Nickel (II) chloride, the sequence of colour change observed will be :
  1. Violet $\rightarrow$ Blue $\rightarrow$ Pale Blue $\rightarrow$ Green
  2. Pale Blue $\rightarrow$ Blue $\rightarrow$ Green $\rightarrow$ Violet
  3. Green $\rightarrow$ Pale Blue $\rightarrow$ Blue $\rightarrow$ Violet
  4. Pale Blue $\rightarrow$ Blue $\rightarrow$ Violet $\rightarrow$ Green

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
$\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_2(\mathrm{en})\right]_{(\mathrm{aq})}^{+2}+\mathrm{en}_{(\mathrm{aq})} \rightarrow\left[\mathrm{Ni}(\mathrm{en})_3\right]_{(\mathrm{aq})}^{+2}+2 \mathrm{H}_2 \mathrm{O}$
Blue / purple

Asked in: JEE Main 2025 (24 Jan Shift 2)

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