When Ethane-1,2-diamine is added progressively to an aqueous solution of Nickel (II) chloride, the sequence of colour change observed will be:
Green Pale Blue Blue Violet
Pale Blue Blue Green Violet
Pale Blue Blue Violet Green
Violet Blue Pale Blue Green
Correct answer:C
Standard Method
Given: Ethane-1,2-diamine is added progressively to an aqueous solution of nickel(II) chloride.
Find: The correct sequence of colour changes.
As ethane-1,2-diamine is added to the solution, the nickel(II) complex undergoes changes in coordination, resulting in a series of colour transitions. Initially, the solution is pale blue and then turns blue, followed by violet, and finally green.
Therefore, the sequence of colour change is Pale Blue Blue Violet Green.
The correct option is C.
Assuming the initial colour is green because nickel(II) salts are often remembered as green is incorrect here. The question specifically concerns the aqueous nickel(II) species, which is taken as pale blue in the given solution. Start from the hydrated ion present in water.
Confusing the order of intermediate complexes is a common error. The colour change must follow the progressive replacement of water by ethane-1,2-diamine, so do not jump directly from blue to green without the violet stage.
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