Questions from Previous Chemistry 116 Exams

Coordination Chemistry

1. 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, oC1 78.5 -117.32 -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)4

2+ 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) <=> 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)6

2+ 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)6

2+, 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 Isomersii. Geometric Isomersiii. 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)6

3-]? (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)6

2+ and CoCl42-:

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.

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, FeF6

3- and Fe(CN)6

3-.

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 colored but coordination compounds containing Cu+ are not?

a. The 3d orbitals in Cu+ are completely empty so the transfer of an electron cannot occur.

b. The 3d orbitals in Cu2+ are completely filled so the transfer of an electron can occur.

c. The 3d orbitals in Cu+ are completely filled so the transfer of an electron cannot occur.

d. Cu+ absorbs all wavelengths of visible light which makes it appear colorless.

e. Cu2+ does not absorb any wavelengths of visible light. 30. What are the oxidation number (ON) and coordination number (CN) of iron in the

coordination compound K4[Fe(CN)6]? a. ON = 2, CN = 2 b. ON = 2, CN = 4 c. ON = 2, CN = 6 d. ON = 3, CN = 6 e. no response is correct

31. Given that nickel metal can be written as [Ar] 4s2 3d8, which is the correct representation for the Ni2+ ion.

a. [Ar] 4s0 3d8 b. [Ar] 4s2 3d6 c. [Ar] 4s1 3d7 d. [Ar] 4s0 3d5 e. correct response not given

Use the following information to answer questions 31, 32 and 33 related to the crystal-field theory of coordination compounds.

Ferric ion (Fe3+) forms the complexes FeF63- and Fe(CN)6

3- with fluoride (F-) and cyanide (CN-) ions. Also, F- is a weaker-field ion than is CN- in the spectrochemical series, i.e., F- < ..... < CN-.

32. We would expect FeF63- to:

a. have a larger crystal field splitting energy than Fe(CN)63-.

b. have a smaller magnetic moment than Fe(CN)63-.

c. absorb light at a longer wavelength (lower energy) than Fe(CN)63-.

d. be more soluble than Fe(CN)63-.

33. We would expect Fe(CN)63- to:

a. have a smaller crystal-field splitting energy than FeF63-.

b. have a smaller magnetic moment than FeF63-.

c. absorb light at a longer wavelength (lower energy) than FeF63-.

d. be more soluble than FeF63-.

34. We would expect both FeF63- and Fe(CN)6

3- to form: a. linear structures. b. tetrahedral structures. c. square planar structures. d. octahedral structures.

35. What is the oxidation state of chromium, AND the coordination number, for the coordination compound, [Cr(en)2(OH)2]Cl?

a. +2, 4 b. +3, 4 c. +3, 5 d. +3, 6 e. +5, 6

36. All coordination compounds which contain a Zn2+ transition metal ion are colorless. Which of the following statements best explains this observation?

a. Zn2+ contains unpaired electrons so it should be colorless.

b. All of the 3d orbitals in Zn2+ are filled; therefore, the transfer of an electron cannot occur.

c. Compounds containing Zn2+ absorb only blue light so they appear colorless.

d. Compounds containing Zn2+ absorb only red light so they appear colorless. e. There is insufficient information to explain this observation.

37. Coordination compounds which contain cyanide, CN-, ligands tend to be yellow whereas coordination compounds which contain water, H2O, ligands tend to be blue or green because:

a. the complexes diffract light at different angles. b. cyanide is a weak-field ligand and water is a strong-field ligand. c. cyanide is a strong-field ligand and water is a weak-field ligand. d. cyanide compounds absorb yellow light and water compounds absorb blue

or green light. e. The basic premise of the question is incorrect because both water and

cyanide are colorless and accordingly cannot influence the color of the coordination compounds.

38. In the Qualitative Analysis scheme, the confirmatory test for the Co2+ ion was the formation of the blue Co(SCN)4

2- complex ion. Assume that the SCN- ligand is a strong-field ligand and that this species is tetrahedral, and determine the number of unpaired electrons in this complex ion.

a. 1 b. 2 c. 3 d. 4 e. 5

39. In the crystal field model for an octahedral complex, the dz2 and dx2-y2 orbitals (eg set) are at higher energy than the dxy, dxz and dyz orbitals (t2g set). Which one of the following statements best explains this behavior?

a. The eg orbitals experience less electrostatic repulsion with the negative point charges than the t2g orbitals.

b. The eg orbitals experience more electrostatic repulsion with the negative point charges than the t2g orbitals.

c. The t2g orbitals point directly at the negative point charges. d. The splitting of the two sets of orbitals is also present in the free ion and

therefore the negative point charges have no effect. e. The eg orbitals are at higher energy because there are only two of them.

40. What is the oxidation state of the metal ion in the complex Ni(NH3)6Cl2? a. -1 b. 0 c. +1 d. +2 e. +3

41. How many total isomers (structural isomers and stereoisomers) exist for the complex ion [Co(NH3)5Cl]2+?

a. 1

b. 2 c. 3 d. 4 e. 6

42. Which of the following compounds would be paramagnetic? a. Sc(NH3)6

3+ (high spin) b. Zn(OH)4

2- (tetrahedral) c. Co(NH3)6

3+ (high spin) d. Fe(CN)6

4- (low spin) 43. Why are many coordination compounds colored?

a. The equilibrium established between the coordination compounds and air lies on the product side.

b. The energy required to excite an electron to an excited state is often the same as the energy of light in the visible region.

c. The Crayola Corporation likes it that way. d. They all absorb water vapor, which normally hides all of the colors.

44. Calculate the crystal field stabilization energy (in terms of Dq) for the high-spin complex Fe(H2O)6

3+. a. -20 Dq b. -16 Dq c. -8 Dq d. -3 Dq e. 0 Dq

45. The following figure shows a complex ion that has a charge of 2-:

a. What part of the complex ion functions as a Lewis base? b. What is the ligand in this complex ion? c. What is the coordination number of this complex ion? d. What is the correct name for the geometry of this complex ion? e. What is the oxidation state of the central metal atom? f. This complex ion is colorless. Explain why.

46. Consider the coordination compound, Na3[Co(CN)6]. Would you expect this compound to be diamagnetic or paramagnetic? Explain your reasoning. You may assume that the CN- ligand is a strong-field ligand.

47. What is the coordination number and the charge on the transition-metal ion expressed as {coord. no., charge} in this complex: Co(CN)2(en)(NH3)2

+. (Note: 'en' represents ethylenediamine, a bidentate molecule.)

a. {5, 1+} b. {5, 3+} c. {6, 1+} d. {6, 3+} e. {7, 1+}

48. According to crystal field theory, the color associated with most coordinated complexes of transition-metal ions arises from the splitting of the degenerate d-orbitals when placed in a ligand field. For the purpose of our discussion, the following are transition-metal ions. Which one would most likely be colorless in an aqueous solution?

a. Fe2+ b. Co2+ c. Ni2+ d. Cu2+ e. Zn2+

49. In hemoglobin, the Fe2+ coordinates with O2. The oxygenated Fe2+ is diamagnetic. This measured diamagnetism means that O2 is a __________ ligand, forming a __________ complex.

Which answer correctly fills in the above blanks?

a. strong-field ------- low-spin b. weak-field ------- low-spin c. weak-field ------- high-spin d. strong-field ------- high-spin

50. To form a coordination bond, one needs a ligand. Which of the following species cannot be a ligand?

a. NH4+

b. NO2-

c. Cl- d. H2O

51. Concerning a coordinated complex, which of the following statements is not true? a. The coordination number is a function of the charge on the metal ion

involved. b. Some coordinated complexes use metal ions which are not transition-

metal ions. c. The coordination number is the number of individual species involved in

the coordination. d. The coordination number is a function of the specific metal ion involved.

52. What is the color of an aqueous solution containing Zn(NH3)42+?

a. blue b. yellow c. red d. plaid e. colorless

53. The following figure shows a complex ion that has a charge of 1-:

a. What part of the complex ion functions as a Lewis acid? b. What is/are the ligand(s) in this complex ion? c. What is the coordination number of this complex ion? d. What is the correct name for the geometry of this complex ion? e. What is the oxidation state of the central metal atom? f. This complex ion is colorless. Briefly explain why this complex ion is

colorless. g. The complex ion Fe(CN)6

3- is paramagnetic and has one unpaired electron. The complex ion Fe(SCN)6

3- is also paramagnetic but has five unpaired electrons. Briefly explain why the Fe(SCN)6

3- complex ion has so many more unpaired electrons compared to the Fe(CN)6

3- complex ion. Hint: a picture is worth a thousand words (although you should use some words to explain the picture)!

h. What is the coordination number and the charge on the transition metal ion expressed as {coord. no., charge} in this complex: Ni(en)2(H2O)2

2+? Note: "en" represents ethylenediammine, a bidentate ligand.

.a {4, 2+}

.b {4, 4+}

.c {5, 4+}

.d {6, 2+}

.e {6, 4+} b. A ligand is needed to form a coordinate covalent bond. Which of the

following species CANNOT be a ligand? .a NH3 .b CN- .c Na .d Br-

.e H2O c. The coordination compound, Pt(NH3)2Cl2, has a square-planar structure

and is used medicinally as an anti-cancer drug. The square-planar shape of this molecule is determined primarily by the number and arrangement of which of the following?

.a positrons

.b protons

.c neutrons

.d electrons

.e quarks d. What is the relationship between the following two complex ions?

I. [Co(NH3)4(NO2)Cl]+

II. [Co(NH3)4(ONO)Cl]+

The complex ions are:

.a coordination isomers.

.b optical isomers.

.c linkage isomers.

.d geometric isomers.

.e the same. e. What are the oxidation number of the iron atom, coordination number and

geometric shape, respectively, for the complex ion, [Fe(CN)6]4-? .a +2 ; 6 ; octahedral .b +2 ; 4 ; tetrahedral .c +3 ; 6 ; octahedral .d +3 ; 4 ; square planar .e It is impossible to tell.

f. The electron configuration for cobalt in the zero oxidation state is: [Ar]4s23d7. What is the correct valence-bond representation for the complex ion, Co(NH3)6

3+? (Note: Pairs of arrows in brackets correspond to pairs of electrons from the ligand.)

g. In the experiment, "How Much Copper Is In a Penny? Part 1.", you determined the concentration of copper in aqueous solutions containing both Cu(NH3)4

2+ and Zn(NH3)42+ by measuring the absorbance of the

solution. Which of the following statements best describes why the

presence of Zn(NH3)42+ did not interfere with the spectrophotometric

measurements for copper? .a The concentration of Zn(NH3)4

2+ was too low to be detected. .b The concentration of Zn(NH3)4

2+ was too high to be detected. .c Zn(NH3)4

2+ is a colorless complex ion. .d The path length of the cuvette needed to be twice as large in order

to be able to detect Zn(NH3)42+.

.e None of the these statements is correct. h. Which one of the following is the correct electron configuration for the

cobalt atom in [Co(NH3)4(OH2)2]3+? .a [Ar] 4s2 3d7 .b [Ar] 4s1 3d5 .c [Ar] 4s1 3d4 .d [Ar] 3d7 .e [Ar] 3d6

i. Which of the following types of isomers can the square planar complex ion, [NiBr4]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. b. For the complex ion, [Co(en)2(OH2)CN]2+, what are the coordination

number (C.N.) and the oxidation number (O.N.) of the central metal atom? .a C.N. = 4 ; O.N. = +2 .b C.N. = 4 ; O.N. = +3 .c C.N. = 4 ; O.N. = +6 .d C.N. = 6 ; O.N. = +2 .e C.N. = 6 ; O.N. = +3

c. How many geometric isomers exist for the tetrahedral complex ion [CoCl2Br2]2-?

.a 0

.b 1

.c 2

.d 3

.e 4 d. How many unpaired electrons are there in the complex ion [Cr(NO2)6]4-?

You may assume that NO2- is a strong-field ligand.

.a 0

.b 1

.c 2

.d 3

.e 4 e. Assume two octahedral coordination compounds, each containing the

same central metal ion with five unpaired d electrons (eg. Fe3+). One compound contains a low-field ligand (eg. F-) and the other compound contains a high-field ligand (eg. CN-). Compared to the high-field compound, it is expected that the low-field compound would have a:

.a smaller magnetic moment and absorb higher energy light.

.b smaller magnetic moment and absorb lower energy light.

.c larger magnetic moment and absorb higher energy light.

.d larger magnetic moment and absorb lower energy light. f. How many unpaired electrons are there in Ni(NH3)4Cl2? You may assume

that this is a strong-field compound. .a zero .b one .c two .d three .e four

g. Ferric ion (Fe3+, [Ar]3d5) forms the complex ions, FeF63- and Fe(CN)6

3-. Given that F- is a "weak-field" ligand and CN- is a "strong-field" ligand, compare the magnetic and light absorption properties of the F- complex to those of the CN- complex. Relative to the CN- complex, the fluoride complex:

.a is less paramagnetic and absorbs at shorter wavelengths (higher energy).

.b is more paramagnetic and absorbs at shorter wavelengths (higher energy).

.c is more paramagnetic and absorbs at longer wavelengths (lower energy).

.d is less paramagnetic and absorbs at longer wavelengths (lower energy).

h. What is the oxidation state of the metal atom in [Co(NH3)4Cl2]Cl and how many moles of ions are formed when 1 mole of this compound dissolves in water?

.a +3 ; 2 moles

.b +1 ; 2 moles

.c +2 ; 2 moles

.d +3 ; 4 moles

.e +6 ; 4 moles i. How many unpaired electrons are there in the complex ion, Cr(CO)6

3+, if carbon monoxide, CO, is a strong-field ligand?

.a 0

.b 1

.c 2

.d 3

.e 4

j. What is the oxidation state of copper, AND the coordination number, for the coordination compound, [Cu(NH3)4]SO4?

.a +1, 4

.b +2, 4

.c +2, 5

.d +3, 4

.e +3, 5 k. Which of the following metal ions would be expected to form

COLORLESS coordination compounds? .a Ti3+ .b Cr3+ .c Mn2+ .d Co2+ .e Cu+

l. How many unpaired electrons are there in the coordination compound, Na3[Co(CN)6]?

.a 0

.b 1

.c 2

.d 3

.e 4 m. What is the oxidation state of the metal atom in [Co(NH3)4]Cl3 and how

many moles of ions are formed when 1 mole of this compound dissolves in water?

.a +3 ; 2 mols

.b +1 ; 2 mols

.c +2 ; 2 mols

.d +3 ; 4 mols

.e +6 ; 4 mols n. Using the absorbance and concentration data provided below for

[Cu(NH3)4]2+ (obtained using a Spectronic 20 set at 580 nm with a path length of 1.00 cm), calculate the molar absorptivity for [Cu(NH3)4]2+ (in M-1 cm-1) at 580 nm.

flask absorbance concentration, M1 0.222 3.7 x 10-3

2 0.427 7.1 x 10-3

3 0.720 1.2 x 10-2

o. In the lab, you measured the absorbance of [Cu(NH3)4]2+ at 580 nm in solutions containing both [Cu(NH3)4]2+ and [Zn(NH3)4]2+. Which of the following best explains why the presence of [Zn(NH3)4]2+ does not interfere with the measurements?

.a The concentration of [Zn(NH3)4]2+ in the solutions was much smaller than the concentration of [Cu(NH3)4]2+.

.b The molar absorptivity of [Zn(NH3)4]2+ at 580 nm was greater than 5000.

.c The path length of the cuvette was too small to allow [Zn(NH3)4]2+ to absorb visible light.

.d [Zn(NH3)4]2+ does not absorb light in the visible region of the electromagnetic spectrum.

.e None of the above are true. p. When one mole of the coordination compound, [Co(NH3)5Cl]Cl2, is

dissolved completely in water, how many moles of ions are produced? .a 0 .b 1 .c 2 .d 3 .e 4

q. Which of the following best explains why chloride ion is a monodentate ligand?

.a A chloride ion has only one unshared pair of electrons that it can use to form a coordinate covalent bond to a metal atom.

.b A chloride ion has only one electron with which to form a coordinate covalent bond to a metal atom.

.c A chloride ion has two unshared pairs of electrons, but both unshared pairs of electrons are used to form a single coordinate covalent bond to a metal atom.

.d A chloride ion has four unshared pairs of electrons, but the other unshared pairs are not close enough to a second coordination site to form a coordinate covalent bond.

.e None of these. r. Consider the following octahedral complex ion,

Which of the following statements about this complex ion is TRUE?

.a The complex ion can exist as both geometric isomers and optical isomers.

.b The complex ion can exist as both linkage isomers and geometric isomers.

.c The complex ion can exist only as optical isomers.

.d The complex ion can exist only as geometric isomers.

.e The complex ion cannot exist as either geometric or optical isomers.

s. Which of the following common shapes (I-IV) can never exist as geometric isomers, regardless of the identity of the ligands?

.. linear ... square planar

.... tetrahedral

.V. octahedral

.a I only

.b I and II

.c I and III

.d II and IV

.e III only b. Which of the following best explains why ammonia is a monodentate

ligand? .a An ammonia molecule has only one unshared pair of electrons that

it can use to form a coordinate covalent bond to a metal atom. .b An ammonia molecule has only one electron with which to form a

coordinate covalent bond to a metal atom. .c An ammonia molecule has two unshared pairs of electrons, but

both unshared pairs of electrons are used to form a single coordinate covalent bond to a metal atom.

.d An ammonia molecule has four unshared pairs of electrons, but the other unshared pairs are not close enough to a second coordination site to form a coordinate covalent bond.

.e None of these.

Answers1. C 2. A 3. E 4. E 5. E 6. A 7. E 8. D 9. E 10. A 11. C 12. C

13. D 14. E 15. E 16. E 17. A 18. D 19. C 20.

.. The cobalt atom in both complex ions is in a +2 oxidation state. This corresponds to an electronic configuration of: [Ar]3d7. The complex ion, [Co(OH2)6]2+, is octahedral and the complex ion, CoCl4

2-, is tetrahedral. .. |.. _____ _____.D.. | |

|.F _____ _____

_____.G.G || || || ||

||.._____ _____ _____ _____

_____J.K.L. [Co(OH2)6]2+ CoCl4

2-

..large crystal field splitting small crystal field splitting

N. strong-field case weak-field case

.. Both of these complex ions are paramagnetic because both species contain unpaired electrons.

2. D 3. B 4. B 5. A 6. D 7. E 8. A 9. C 10. C 11. A 12. C 13. B 14. D 15. D 16. B 17. C

18. C 19. B 20. D 21. A 22. C 23. B 24. E 25.

.a The ligands. They donate pairs of electrons.

.b Cyanide ion, CN-.

.c Four.

.d Tetrahedral.

.e +2.

.f The electronic configuration of Zn2+ is [Ar]3d10. Thus, all of the d orbitals are COMPLETELY filled and the transition of an electron cannot occur (nowhere for it to go!).

2. Here, the coordination number is equal to 6. Therefore, the complex ion has an octahedral geometry. Moreover, CN- is a strong-field ligand. Finally, the oxidation state of the metal is +3, so the electronic configuration is: [Ar]3d6. Placing the 6 d electrons into a strong-field, octahedral crystal field leads to double occupancy of each of the lower t2g set of d orbitals. The compound should thus be diamagnetic (all electrons paired).

3. D 4. E 5. A 6. A 7. C 8. E 9.

.a The transition metal. Here, Cu.

.b Ammonia, NH3, and chloride, Cl-.

.c Four.

.d Square planar.

.e +1

.f The electronic configuration of Cu+ is: [Ar]3d10. Regardless of the geometry (and therefore the crystal field diagram), all of the 3d orbitals are filled. There can be no electronic transition between the split d orbitals.

2. The iron atom in both complex ions is in a +3 oxidation state. This corresponds to an electronic configuration of: [Ar]3d5. Also, both ions are octahedral.

3. _____ _____4.5. | |

6. _____ _____7.8. || || | | |

|9. _____ _____ _____ _____ _____

_____10.11.12. Fe(CN)6

3- Fe(SCN)63-

13. large crystal field splitting small crystal field splitting

14. strong-field case weak-field case

Because the t2g and eg sets of d orbitals in the weak-field case are so close in energy, one can put an electron into each orbital before pairing. This is not possible in the strong-field case as the eg orbitals are much higher in energy; therefore the electrons must pair up.

15. D 16. C 17. D 18. C 19. A 20. A 21. C 22. E 23. E 24. E 25. A 26. C 27. D 28. C 29. C 30. A 31. D 32. B 33. E 34. A 35. D 36. 60 37. D 38. D 39. D 40. D 41. C 42. A