Questions From Previous Chemistry 116 Exams

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Questions from Previous Chemistry 116 Exams Coordination Chemistry1. What are the geometric shape and the oxidation number of the copper atom, respectively, for the complex ion, [Cu(NH3)4(OH2)2]2+? a. tetrahedral ; +2 b. square planar ; -2 c. octahedral ; +2 d. linear ; +3 e. trigonal planar ; +1 2. What is the relationship between the following two linear complex ions?

The complex ions are: a. linkage isomers b. coordination isomers c. geometric isomers d. optical isomers e. the same 3. Consider the experimental data below for compounds 1 and 2 which have the same molecular formula, C2H6O, compound boiling point, oC freezing point, oC 1 78.5 -117.3 2 -25.0 -138.5 4. Which of the following statements is TRUE? a. Compounds 1 and 2 are not isomers. b. Compounds 1 and 2 are optical isomers. c. Compounds 1 and 2 have identical physical properties. d. All of the above are TRUE. e. None of these is TRUE. 5. What is the relationship between the following two square planar complex ions?

The complex ions are: a. linkage isomers b. coordination isomers c. geometric isomers d. optical isomers e. the same 6. What are the oxidation number (ON) and coordination number (CN) in the coordination compound, [Cu(en)(NH3)2]Cl2? (Be careful.) a. ON = 1, CN = 1 b. ON = 1, CN = 2 c. ON = 2, CN = 2 d. ON = 2, CN = 3 e. ON = 2, CN = 4 7. The electron configuration for nickel in the zero oxidation state is [Ar]4s23d8. Which of the following is the correct valence-bond representation of the complex ion, Ni(CN)4-2 ? Note: Unfilled circles represent two paired electrons from nickel and filled circles represent two paired electrons from the cyanide ion.

8. Which one of the following is the correct electron configuration for the Fe3+ ion? a. [Ar] 4s1 3d5 b. [Ar] 4s2 3d3 c. [Ar] 4s1 3d4 d. [Ar] 3d6 e. [Ar] 3d5 9. Which one of the following best explains why water is a monodentate ligand? a. 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. b. Each hydrogen atom in a water molecule has only one electron with which to form a coordinate covalent bond to a metal atom. c. 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.

d. 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. e. None of these. 10. What are the coordination number and the oxidation state, respectively, of the cobalt atom in the compound [Co(NH3)5Cl]Cl2? a. 4 ; +2 b. 4 ; +3 c. 5 ; +2 d. 6 ; +2 e. 6 ; +3 11. "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. a. 0 b. 1 c. 2 d. 3 e. 4 12. 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? a. The Zn atom does not have any 3d electrons; thus, an electron cannot be transferred between the split 3d orbitals. b. The Zn atom does not have any 4s electrons; thus, an electron cannot be transferred between the split 4s orbitals. c. The 3d orbitals on the Zn atom are completely filled; thus, an electron cannot be transferred between the split 3d orbitals. d. The Zn atom does not have any unpaired electrons which are necessary in order to transfer an electron between the split 3d orbitals. e. The Zn(NH3)42+ ion only absorbs blue light which makes the solution colorless. 13. When solid CoCl2 is dissolved in water, a pink solution results and the following equilibrium is established: Co(H2O)62+ (aq) + 4 Cl- (aq) CoCl42- (aq) + 6 H2O (l) I. In aqueous solution, the Co(H2O)62+ ion is pink, and the CoCl42- ion is blue. II. The shape of Co(H2O)62+ is octahedral whereas the shape of CoCl42- 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?

a. Because a solution of HCl is colorless, the color of the CoCl2 solution will not change. b. Because HCl is a strong acid, the number of unpaired electrons in Co(H2O)62+, but not CoCl42-, will change. c. The concentration of Co(H2O)62+ will decrease and the concentration of CoCl42- will increase; the color of the solution will become more blue. d. The concentration of Co(H2O)62+ will increase and the concentration of CoCl42- will decrease; the color of the solution will become more pink. e. The addition of HCl will have no effect on the position of the equilibrium. 14. Which one of the following can form geometric isomers? a. [AgCl2]b. [Cu(NH3)4]2+ (square planar) c. [Co(OH2)5Cl]2+ d. Ni(OH2)2Br2 (square planar) e. None of these can form geometric isomers. 15. Which of the following types of isomers can [Ag(NH3)2]+ form? i. Linkage Isomers ii. Geometric Isomers iii. Optical Isomers a. i only b. i and ii c. i and iii d. iii only e. None of these. 16. What color would we expect an aqueous solution containing Ti(OH2)44+ to be? a. blue b. red c. green d. yellow e. colorless 17. What is the oxidation number of platinum in the coordination compound, Pt(NH3)2Cl2? a. -2 b. -1 c. 0 d. +1 e. +2 18. 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.) a. C. N. = 6, O. N. = +2. b. C. N. = 5, O. N. = +2. c. C. N. = 4, O. N. = +3. d. C. N. = 4, O. N. = +2.

e. C. N. = 3, O. N. = +1. 19. What is the relationship between the following two square-planar compounds? The compounds are:

a. linkage isomers b. optical isomers c. coordination isomers d. geometric isomers e. the same 20. 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)63-]? (Answer format: electron configuration ; hybrid bonds) a. [Ar]4s23d6 ; sp2 b. [Ar]4s3d4 ; sp2 c. [Ar]3d5 ; sp3d2 d. [Ar]3d6 ; sp3d2 e. [Ar]3d5 ; sp2 21. 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 CoCl42-: Co(OH2)62+ (pink) + 4 Cl- CoCl42- (dark blue) + 6 H2O A. Draw the crystal field splitting diagrams for BOTH Co(OH2)62+ and CoCl42-. You may assume that water is a strong-field ligand, and that CoCl42- has a tetrahedral structure. B. Which of these complex ions (i. e. , Co(OH2)62+ or/and CoCl42-.) is/are paramagnetic? Briefly explain your reasoning. 22. What is the coordination number, C.N., for the central metal ion in the coordination compound, K3[Fe(CN)6]? a. C.N. = 3 b. C.N. = 4 c. C.N. = 5 d. C.N. = 6 e. The correct response is not given.

23. Which of the following are all features of optical isomers? Optical isomers are: a. superimposable mirror images with identical chemical formulae and the same chemical reactivities with other compounds that are not optical isomers. b. nonsuperimposable mirror images with identical chemical formulae and the same chemical reactivities with other compounds that are not optical isomers. c. nonsuperimposable mirror images with dissimilar chemical formulae but similar chemical reactivities with other compounds that are not optical isomers. d. superimposable mirror images with identical chemical formulae and similar physical properties. e. 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, FeF63- and Fe(CN)63-. 24. The magnetic moment of the fluoride complex is expected to be: a. the same as the magnetic moment of the cyanide complex. b. larger than the magnetic moment of the cyanide complex because there are more unpaired electrons in the fluoride complex. c. smaller than the magnetic moment of the cyanide complex because there are more unpaired electrons in the fluoride complex. d. larger than the magnetic moment of the cyanide complex because there are fewer unpaired electrons in the fluoride complex. e. The correct response is not given. 25. The energy of light absorbed by the cyanide complex will be: a. greater than that of the fluoride complex because the crystal-field splitting is larger in the cyanide complex. b. less than that of the fluoride complex because the crystal-field splitting is larger in the cyanide complex. c. greater than that of the fluoride complex because the crystal-field splitting is smaller in the cyanide complex. d. similar to that of the fluoride complex because the energy of light absorbed depends only on the central metal ion and is independent of the ligand field strength. e. The correct response is not given.

26. Which of the following is the correct electronic configuration for a Mn4+ ion? a. [Ar] 4s2 3d1 b. [Ar] 4s2 3d4 c. [Ar] 3d4

d. [Ar] 3d3 e. [Ar] 4s1 3d2 27. What is the relationship between the two square planar coordination compounds (A and B) shown below? These compounds are:

a. geometric isomers. b. coordination isomers. c. optical isomers. d. linkage isomers. e. the same. 28. How many unpaired electrons are there in [Co(NH3)4Cl2]Cl? You may assume that this is a strong-field compound. a. zero b. one c. two d. three e. four 29. Which of the following best explains why coordination compounds containing Cu2+ are co