Crystal Field theory questions and simple or brief reasoning of why

Question

I
Which statement most correctly describes crystal field theory for a d block complex of unspecified geometry?

(a) The theory considers covalent interactions between a metal center and the surrounding ligands.

(b) The theory considers electrostatic interaction between a metal ion and the surrounding ligands which are taken to be
point charges

(c) The theory rationalizes the non-degeneracy of the metal d orbitals by considering the electrostatic repulsion between point charge ligands and electrons in the metal d orbitals.

(d ) the theory rationalizes why the metal d orbitals are split into two levels.


II

Which of the following correctly places the ligands in their order in the spectrochemical series?

(a) Br-< Cl-< NH3< H2O

(b) I- < Br- < H2O < [OH]-

(c) F- < Cl- < H2O < NH3

(d) I-< Cl-< H2O < en

 

III

 

Which of the following correctly places the metal centers in order of increasing field strength?

 

(a)  Mn(II) <Fe(III) <Rh(III)

 

(b)  Co(III) <Co(II)<Rh(III)

 

(c)  Pt(IV)  <Pd(II) <Ni(II)

 

(d)  Pd(II) <Ni(II)  <Pt(IV)

 

IV

 

(a) [PdCl₄]^2-

 

(b) [PtCl₄]^2-

 

(c) [NiCl₄]^2-

 

(d) [AuCl₄]^2-

 

V

 

Match up the correct formula and magnetic property. Which pair correct?

 

(a) [Zn(H₂O)₆]²⁺; paramagnetic

 

(b) [Co(NH₃)₆]³⁺ ; diamagnetic

 

(c) [CoF₆]^3- ; diamagnetic

 

(d) [V(H₂O)₆]²⁺ ; diamagnetic

Answer 1

Of the options presented for 1 a is the best answer. Crystal field theory only considers ligands as point charges and it allows us to understand why the d orbitals break degeneracy.

2. d - honestly this one might be easier to just check the list.

3. a - in terms of metal ligand field strength there are a couple rules to keep in mind. smaller charge < larger charge and 3d<4d<5d metals. a obeys both rules.

4 no question provided.

5 b. For this you should first find your d count. Zn2+ is d10 so all orbitals must be doubly filled. so it is diamagnetic. V2+ is d3 and so has an odd number of electrons and must be paramagnetic. Co3+ is d6 and depends on the ligands. F- is a weak field ligand so would be high spin paramagnetic. NH3 is a stronger field ligand so low spin and diamagnetic.