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Which of the following is a coloured compound?
(A) CuF2
(B) CuI
(C) NaCl
(D) MgCl2

Answer
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Hint: The transition metal compounds are often colored because of transition of electrons between d orbitals of different energy. The d block elements having unpaired electrons form coloured compounds.

Complete step by step solution:
When a visible light falls on a transition metal compound or ion, the unpaired electrons present in the lower energy d-orbital get promoted to higher energy d-orbital. This is called a d-d transition.
Therefore, the transmitted light shows the same color complementary to the absorbed color.
Therefore in CuF2
The electronic configuration of Cu is
=1s22s22p63s23p64s03d9
Thus, it has one unpaired electron.
So, it has one unpaired electron and hence, CuF2 is a coloured compound.
It is a white crystalline, hygroscopic solid with a rutile-type crystal structure.

Hence, option A is correct.

Note: Copper fluoride can be used to make fluorinated aromatic hydrocarbons by reacting with aromatic hydrocarbons in an oxygen- containing atmosphere at temperatures above 450C. This reaction is only effective in making compounds that can survive at the temperature used.