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

Answer

Correct option: C.
Green $\rightarrow$ Pale Blue $\rightarrow$ Blue $\rightarrow$ Violet
(C) Green $\rightarrow$ Pale Blue $\rightarrow$ Blue $\rightarrow$ Violet
Sol. $
\left[Ni\left(H_2 O\right)_6\right]^{+2}{ }_{(aq)}+en_{(aq)} \rightarrow\left[Ni\left(H_2 O\right)_4(en)\right]_{(sq)}+2 H_2 O
$
Green$
\left[Ni\left(H_2 O\right)_4(en)\right]_{(a aq)}^{+2}+en_{(a 4)} \rightarrow\left[Ni\left(H_2 O\right)_2(en)_2\right]_{(aq4)}^{+2}+2 H_2 O
$
Pale Blue
$
\left[Ni\left(H_2 O\right)_2(en)\right]_{(aq)}^{+2}+en_{((aq)} \rightarrow\left[Ni(en)_3\right]_{(aq)}^{+2}+2 H_2 O
$
Blue / purple

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