JEE Main · 2021 · 26 Aug 2021 · Shift 1 · d and f Block Elements

Which one of the following when dissolved in water gives coloured solution in nitrogen atmosphere?

Answer: (D)

Solution

Colour in a simple aqueous salt solution requires a partly filled

d

subshell.

C u_{2} C l_{2}

contains

C u^{+}

and

ZnC l_{2}

contains

Z n^{2 +}

, both

3 d^{10}

, so both give colourless solutions, and the nitrogen atmosphere is specified precisely to stop

C u^{+}

being air-oxidised to the coloured

C u^{2 +}

. Silver chloride is insoluble in water and leaves no ions in solution.

CuC l_{2}

dissolves to give

[Cu (H_{2} O)_{6}]^{2 +}

, in which

C u^{2 +}

3 d^{9}

, and the

d

d

transition of this ion makes the solution blue. The compound that gives a coloured solution is

CuC l_{2}

JEE Main · 2021 · 26 Aug 2021 · Shift 1 · Single correct option