The complexes V(C₆H₆)₂ and Cr(C₆H₆)₂ are both readily oxidized in air to their respective cations. The number of unpaired electrons, respectively in each are

The separation of trivalent lanthanide ions, Lu³⁺, Yb³⁺, Dy³⁺, Eu³⁺ can, be effectively done by a cation exchange resin using ammonium o-hydroxy iso-butyrate as the eluent. The order in which the ions will be separated is

A. Lu³⁺, Yb³⁺, Dy³⁺, Eu³⁺

B. Eu³⁺, Dy³⁺, Yb³⁺, Lu³⁺

C. Dy³⁺, Yb³⁺, Eu³⁺, Lu³⁺

D. Yb³⁺, Dy³⁺, Lu³⁺ , Eu³⁺

[CoCl₄]^2- is a blue coloured complex. Controlled-treatment of this complex with water generates two isomeric light pink coloured complexes of composition [Ca(H₂O)₄Cl₂]. Identify the correct point groups far [CoCl₄]^2- and two isomeric complexes [CO(H₂O)₄Cl₂].

A. D_4h and (C_2v and C_2h)

B. T_d and (C_2v and D_4h)

C. D_4h and (C_2v and D_4h)

D. T_d and (C_2v and C_4v)

The complex that exists as a pair of enantiomers is

A. trans-[CO(H₂NCH₂CH₂NH₂)₂Cl₂]⁺

B. cis-[Co(NH₃)₄Cl₂]⁺

C. [Pt(PPh₃)(Cl)(Br)(CH₃)]^-

D. [Co(H₂NCH₂CH₂NH₂)₃]³⁺

The complex formed in the brown ring test for nitrates is

A. [Fe(H₂O)₅NO]³⁺

B. [Fe(H₂O)₅NO]²⁺

C. [Fe(H₂O)₄(NO)]²⁺

D. [Fe(H₂O)₄(NO)]³⁺