Among the following pair of metal ions present in nature, the first one functions as an electron transfer agent and the second one catalyzes the hydrolysis reactions. The correct pair is

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⁺