1. Which one of the following is the correct electron configuration for the Fe³⁺ ion?

    

   1. [Ar] 4s¹ 3d⁵
   2. [Ar] 4s² 3d³
   3. [Ar] 4s¹ 3d⁴
   4. [Ar] 3d⁶
   5. [Ar] 3d⁵

    

2. Which one of the following best explains why water is a monodentate ligand?

    

   1. The oxygen atom in a water molecule only has one lone pair of electrons that it can use to form a coordinate covalent bond to a metal atom.
   2. Each hydrogen atom in a water molecule has only one electron with which to form a coordinate covalent bond to a metal atom.
   3. The oxygen atom in a water molecule has two lone pairs of electrons, but both pairs are used to form a single coordinate covalent bond to a metal atom.
   4. The oxygen atom in a water molecule has two lone pairs of electrons, but the second lone pair is not close enough to a second coordination site to form a coordinate covalent bond.
   5. None of these.

    

3. What are the coordination number and the oxidation state, respectively, of the cobalt atom in the compound [Co(NH₃)₅Cl]Cl₂?

    

   1. 4 ; +2
   2. 4 ; +3
   3. 5 ; +2
   4. 6 ; +2
   5. 6 ; +3

    

4. "Cobalt Yellow" is a pigment used in oil paints, and contains the coordination compound K₃[Co(NO₂)₆]. How many unpaired electrons are there on the cobalt atom in this compound? Note that NO₂^- is a strong-field ligand.

    

   1. 0
   2. 1
   3. 2
   4. 3
   5. 4

    

5. When a concentrated solution of NH₃ is added to a solution containing Zn(NO₃)₂, a colorless solution containing the complex ion Zn(NH₃)₄²⁺ results. Which one of the following best explains why this solution is colorless?

    

   1. The Zn atom does not have any 3d electrons; thus, an electron cannot be transferred between the split 3d orbitals.
   2. The Zn atom does not have any 4s electrons; thus, an electron cannot be transferred between the split 4s orbitals.
   3. The 3d orbitals on the Zn atom are completely filled; thus, an electron cannot be transferred between the split 3d orbitals.
   4. The Zn atom does not have any unpaired electrons which are necessary in order to transfer an electron between the split 3d orbitals.
   5. The Zn(NH₃)₄²⁺ ion only absorbs blue light which makes the solution colorless.

    

6. When solid CoCl₂ is dissolved in water, a pink solution results and the following equilibrium is established:

    

   Co(H₂O)₆²⁺ (aq) + 4 Cl^- (aq) <=> CoCl₄^2- (aq) + 6 H₂O (l)

   I. In aqueous solution, the Co(H₂O)₆²⁺ ion is pink, and the CoCl₄^2- ion is blue.
   II. The shape of Co(H₂O)₆²⁺ is octahedral whereas the shape of CoCl₄^2- is tetrahedral.

   Which one of the following best describes what will happen when a concentrated solution of HCl is added to the CoCl₂ solution without changing the volume significantly?

    

   1. Because a solution of HCl is colorless, the color of the CoCl₂ solution will not change.
   2. Because HCl is a strong acid, the number of unpaired electrons in Co(H₂O)₆²⁺, but not CoCl₄^2-, will change.
   3. The concentration of Co(H₂O)₆²⁺ will decrease and the concentration of CoCl₄^2- will increase; the color of the solution will become more blue.
   4. The concentration of Co(H₂O)₆²⁺ will increase and the concentration of CoCl₄^2- will decrease; the color of the solution will become more pink.
   5. The addition of HCl will have no effect on the position of the equilibrium.

    

7. Which one of the following can form geometric isomers?

    

   1. [AgCl₂]^-
   2. [Cu(NH₃)₄]²⁺ (square planar)
   3. [Co(OH₂)₅Cl]²⁺
   4. Ni(OH₂)₂Br₂ (square planar)
   5. None of these can form geometric isomers.

    

8. Which of the following types of isomers can [Ag(NH₃)₂]⁺ form?

   i. Linkage Isomers
   ii. Geometric Isomers
   iii. Optical Isomers

    

   1. i only
   2. i and ii
   3. i and iii
   4. iii only
   5. None of these.

    

9. What color would we expect an aqueous solution containing Ti(OH₂)₄⁴⁺ to be?

    

   1. blue
   2. red
   3. green
   4. yellow
   5. colorless

    

10. What is the oxidation number of platinum in the coordination compound, Pt(NH₃)₂Cl₂?

     

    1. -2
    2. -1
    3. 0
    4. +1
    5. +2

     

11. For the coordination compound, Na₂[Cd(en)(CN)₄], what are the coordination number (C.N.) and oxidation number (O.N.) of the central metal ion. (Note: The letters, en, represent the ligand, ethylenediamine.)

     

    1. C. N. = 6, O. N. = +2.
    2. C. N. = 5, O. N. = +2.
    3. C. N. = 4, O. N. = +3.
    4. C. N. = 4, O. N. = +2.
    5. C. N. = 3, O. N. = +1.
       
       
12. Iron with an oxidation number of zero can be represented as: [Ar]4s²3d⁶. Based on the valence bond theory of bonding in coordination compounds, which of the following would be the correct representation of the electron configuration of the central metal ion and the hybrid bonds formed in the complex ion, [Fe(CN)₆^3-]? (Answer format: electron configuration ; hybrid bonds)

1. [Ar]4s²3d⁶ ; sp²
2. [Ar]4s3d⁴ ; sp²
3. [Ar]3d⁵ ; sp³d²
4. [Ar]3d⁶ ; sp³d²
5. [Ar]3d⁵ ; sp²

• Note: You must answer BOTH Part A and Part B of this question.

  Some old weather forecasting devices utilized the following equilibrium between Co(OH₂)₆²⁺ and CoCl₄^2-:

   

  Co(OH₂)₆²⁺ (pink) + 4 Cl^- <=> CoCl₄^2- (dark blue) + 6 H₂O

  A. Draw the crystal field splitting diagrams for BOTH Co(OH₂)₆²⁺ and CoCl₄^2-. You may assume that water is a strong-field ligand, and that CoCl₄^2- has a tetrahedral structure.

  B. Which of these complex ions (i. e. , Co(OH₂)₆²⁺ or/and CoCl₄^2-.) is/are paramagnetic? Briefly explain your reasoning.

   

• What is the coordination number, C.N., for the central metal ion in the coordination compound, K₃[Fe(CN)₆]?

   

  1. C.N. = 3
  2. C.N. = 4
  3. C.N. = 5
  4. C.N. = 6
  5. The correct response is not given.

   

• Which of the following are all features of optical isomers? Optical isomers are:

   

  1. superimposable mirror images with identical chemical formulae and the same chemical reactivities with other compounds that are not optical isomers.
  2. nonsuperimposable mirror images with identical chemical formulae and the same chemical reactivities with other compounds that are not optical isomers.
  3. nonsuperimposable mirror images with dissimilar chemical formulae but similar chemical reactivities with other compounds that are not optical isomers.
  4. superimposable mirror images with identical chemical formulae and similar physical properties.
  5. The correct response is not given.

   

  ---

  Use the facts that fluoride ion (F^-) is a weak field ligand, cyanide ion (CN^-) is a strong field ligand and that iron in the plus three oxidation state has five 3-d electrons to answer questions 23 and 24 related to the complex ions, FeF₆^3- and Fe(CN)₆^3-.

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http://www.chem.purdue.edu/gchelp/116exams/coord2.html

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