Question

Among the following compound which is both paramagnetic and coloured?

• A. $K_{2}Cr_{2}O_{7}$
• B. $\lbrack Co(SO_{4})\rbrack$
• C. $(NH_{4})_{2}\lbrack TiCl_{6}\rbrack$
• D. $K_{3}\lbrack Cu(CN)_{4}\rbrack$

Answer 1

Answer: (B)

$\lbrack Co(SO_{4})\rbrack$

Answer 2

In $\lbrack Co(SO_{4})\rbrack$ the oxidations state of Co is +2. Configuration of $Co^{2 +} = 3d^{7}$, it has unpaired electrons in 3d-orbitals so it is paramagnetic. Because of incompletely filled d-orbitals it is coloured.