Deck 19: Transition Metals and Coordination Chemistry

Question 1

What is the electron configuration of the Co(II) ion?

A) [Ar]3d⁶
B) [Ar]3d⁷
C) [Ar]4s²3d⁵
D) [Ar]4s²4d²
E) [Ar]4s²3d⁷

Answer 1

[Ar]3d⁷

Question 2

The corrosion of which transition metal results in a characteristic green patina?

A) lead
B) copper
C) chromium
D) silver
E) iron

Answer 2

copper

Question 3

Suppose you are studying coordination compounds of Co(II) with the ligand pyridine (py, C₅H₅N, molar mass = 79.10). You isolate a crystalline compound, and because the only available anions are Cl^- and NO₃^-, you hypothesize that the empirical formula of the coordination compound must be Co_w(py)_x(Cl)_y(NO₃)_z.
You analyze for pyridine (K_b is approximately 10^-9) by dissolving 0.1000 g of the complex in 100 mL of H₂O and titrating with a 0.01 M HCl solution. Which of the following indicators should be used to detect the endpoint? (Assume that the initial concentration of pyridine is approximately 0.01 M.)

A) thymol blue, pH range of color change = 8.0-9.6
B) methyl red, pH range of color change = 4.8-6.0
C) bromophenol blue, pH range of color change = 3.0-4.6
D) bromothymol blue, pH range of color change = 6.0-7.6
E) alizarin yellow, pH range of color change = 10.1-12.0

Answer 3

bromophenol blue, pH range of color change = 3.0-4.6

Question 4

Which of the following coordination compounds will form a precipitate when treated with an aqueous solution of AgNO₃?

A) Na₃[CrCl₆]
B) [Cr(NH₃)₃Cl₃]
C) Na₃[Cr(CN)₆]
D) [Cr(NH₃)₆]Cl₃
E) all of these

Question 5

What transition metal is used in magnets, catalysts, and drill bits?

A) platinum
B) nickel
C) copper
D) cobalt
E) titanium

Question 6

Which transition metal can exist in all oxidation states from +2 to +7?

A) iron
B) vanadium
C) copper
D) manganese
E) chromium

Question 7

How many d electrons are present on the metal ion in the complex ion PtCl₆^2-?

A) 3
B) 8
C) 2
D) 4
E) 6

Question 8

A compound of which transition metal is responsible for the white color of most paper?

A) chromium
B) titanium
C) zinc
D) nickel
E) copper

Question 9

Which of the following is a d⁹ ion?

A) Cu²⁺
B) Zn²⁺
C) Fe²⁺
D) Cr³⁺
E) Cu⁺

Question 10

Which of the metal ions in the following complex ions has a d⁵ electron configuration?

A) [FeCl₆]^4-
B) [Cr(CN)₆]^3-
C) [Ti(H₂O)₆]²⁺
D) [Ni(NH₃)₆]³⁺
E) [Fe(CN)₆]^3-

Question 11

Transition metals show great similarities both within a given period and within a given vertical group.

Question 12

Which of the following statements is true about coordination complexes?

A) When the ligands approach a transition metal ion in an octahedral field, the d_xz, d_yz, and d_xy atomic orbitals are affected the least by the ligands.
B) The metal is a Lewis base and the ligands are Lewis acids.
C) Only complexes with coordination number 6 are found in nature.
D) None of these is true.
E) All of these are true.

Question 13

Which of the following is a d² ion?

A) Mn³⁺
B) Ti⁺
C) Fe³⁺
D) Cr²⁺
E) Ti²⁺

Question 14

What is the maximum oxidation state of chromium?

A) +4
B) +6
C) +3
D) +5
E) none of these

Question 15

Which metal ion has a d⁶ electron configuration?

A) Ti²⁺
B) Mn²⁺
C) Ni²⁺
D) Fe³⁺
E) Co³⁺

Question 16

Suppose you are studying coordination compounds of Co(II) with the ligand pyridine (py, C₅H₅N, molar mass = 79.10). You isolate a crystalline compound, and because the only available anions are Cl^- and NO₃^-, you hypothesize that the empirical formula of the coordination compound must be Co_w(py)_x(Cl)_y(NO₃)_z.
You discover that the complex decomposes in water. You dissolve 0.1000 g of the complex in H₂O and add excess NaHg(SCN)₄, which precipitates Co(II) as CoHg(SCN)₄(s). After the precipitate is washed and dried, its mass is 0.1102 g. How many grams of cobalt are contained in 0.100 g of the complex?

A) 0.0396 g
B) 0.0132 g
C) 0.1102 g
D) 0.437 g
E) 0.0548 g

Question 17

In which of the following complexes does the transition metal have a d⁸ configuration?

A) [Cd(NH₃)₄]²⁺
B) [NiCl₄]^2-
C) [Mn(CN)₆]^3-
D) [Fe(CO)₅]
E) [Cr(H₂O)₆]²⁺

Question 18

A coordination compound of Cu²⁺ can be described as Cu(NH₃)_xSO₄ and is known to contain 29.9% NH₃. What is the value of x?

A) 6
B) 3
C) 4
D) 2
E) none of these

Question 19

Addition of AgNO₃ to aqueous solutions of the complex results in a cloudy white precipitate, presumably AgCl. You dissolve 0.1000 g of the complex in H₂O and perform a precipitation titration with 0.0500 M AgNO₃ as the titrant. Using an electrode that is sensitive to [Ag⁺], you reach the endpoint after 9.00 mL of titrant is added. How many grams of chloride ion were present in the 0.1000-g sample?

A) 4.50 * 10^-4 g
B) 1.77 * 10^-3 g
C) 5.00 *10^-3 g
D) 1.60 * 10^-2 g
E) 6.38 *10^-2 g

Question 20

The phenomenon called the __________ contraction is responsible for the great similarity in atomic size and chemistry between 4d and 5d elements.

A) transition
B) coordination
C) none of these
D) isomeric
E) lanthanide

Question 21

For which of the following metal ions would there be no distinction between low spin and high spin in octahedral complexes?

A) Mn²⁺
B) Fe²⁺
C) Mn³⁺
D) Cu²⁺
E) Fe³⁺

Question 22

Which model(s) account(s) for the magnetism and color of coordination compounds?
I. the localized electron model
II. the crystal fieldmodel

A) both I and II
B) neither I nor II
C) II only
D) I only

Question 23

A metal ion in a high-spin octahedral complex has two more unpaired electrons than the same ion does in a low-spin octahedral complex. Which of the following could the metal ion be?

A) Co³⁺
B) Zn²⁺
C) Co²⁺
D) V²⁺
E) Cu²⁺

Question 24

How many unpaired electrons are there in a complex ion having a d⁵ electron configuration and an octahedral geometry in the weak-field case?

A) 2
B) 1
C) 3
D) 5
E) 4

Question 25

Which of the following statements is true of the crystal field model?

A) The electrons are assumed to be localized.
B) The metal ion-ligand bonds are considered completely ionic.
C) The ligands are treated as negative point charges.
D) The interaction between metal ion and ligand is treated as a Lewis acid-base interaction.
E) None of these statements is true.

Question 26

_____ isomers and _______ isomers are classes of structural isomers.

A) Geometric, optical
B) Geometric, linkage
C) Linkage, geometric
D) Coordination, linkage
E) Coordination, geometric

Question 27

The spectrochemical series is I^- < Br^- < Cl^- < F^- < OH^- < H₂O < NH₃ < en < NO₂^- < CN^-
Which of the following complexes will absorb visible radiation of the highest energy (shortest wavelength)?

A) [Co(OH)₆]^3-
B) [Co(NH₃)₆]³⁺
C) [Co(I)₆]^3-
D) [Co(H₂O)₆]³⁺
E) [Co(en)₃]³⁺

Question 28

Give the number of geometric isomers for the octahedral compound [Ma₂B₂C₂], where A, B, and C represent ligands.

A) 2
B) 1
C) 3
D) 5
E) none of these

Question 29

Which of the following are structural isomers?
I.Coordination isomers
II.Linkage isomers
III.Geometric isomers
IV.Optical isomers

A) II, IV
B) II, III
C) I, II
D) I, III, IV
E) I, III

Question 30

The color of a transition metal complex results from

A) nuclear magnetic resonance.
B) transition of an electron between d orbitals.
C) bending vibrations.
D) stretching vibrations.
E) transition of an electron between an s orbital and a p orbital.

Question 31

For the process Co(NH₃)₅Cl²⁺ + Cl^- $\rightarrow$ Co(NH₃)₄Cl₂⁺ + NH₃, what would be the ratio of cis to trans isomers in the product?

A) 4:1
B) 1:1
C) 2:1
D) 1:2
E) 1:4

Question 32

The complex FeL₆²⁺, where L is a neutral ligand, is known to be diamagnetic. How many d electrons are there in this complex ion?

A) 7
B) 8
C) 6
D) 4
E) 5

Question 33

How many of the following compounds exhibit geometric isomers?
I.Pd(NH₃)₂Br₂ (square planar)
II.[Co(NH₃)₂]Cl₃
III.[Ni(NH₃)₄(NO₂)₂]
IV.K₂[CoBr₄]

A) 2
B) 3
C) 1
D) 4
E) 0

Question 34

Which of the following complexes shows geometric isomerism?

A) K[Co(H₂O)₂Cl₄]
B) [Co(H₂O)₅Cl]Cl₂
C) [Co(H₂O)₅Cl]SO₄
D) Na₃[CoCl₆]
E) [Co(H₂O)₆]Cl₃

Question 35

Fluoride ion ranks low in the spectrochemical series and produces a weak crystal field in complex ions. Based on this information, predict the number of unpaired electrons in [CrF₆]^3-.

A) 0
B) 1
C) 2
D) 5
E) 3

Question 36

Analysis of the data from a titration indicates that a 0.1000-g sample of the complex contains 0.0708 g of py. Further analysis shows that 0.1000 g of the complex contains 0.0132 g of cobalt and 0.0160 g of chloride. What is the empirical formula of the complex?

A) Co(py)₆(Cl) (NO₃)
B) Co(py)₄(NO₃)₂
C) Co₂(py)₅(Cl)₂(NO₃)₂
D) Co₃(py)₈(Cl)₂(NO₃)₄
E) Co(py)₄Cl₂

Question 37

Which of the following statements about the complex ion Co(en)₂Cl₂⁺ is true? (en = ethylenediamine, NH₂CH₂CH₂NH₂)

A) The geometric isomers of the complex ion have identical chemical properties.
B) The complex ion exhibits two geometric isomers (cis and trans) and two optical isomers.
C) Because en is a strong field ligand (large $\Delta$ ), the complex ion is paramagnetic.
D) The complex ion exhibits cis and trans geometric isomers, but no optical isomers.
E) The complex ion contains Co(I).

Question 38

The empirical formula of a compound with a mass percent composition of 6.78% H, 31.43% N, 39.76% Cl, and 22.03% Co is consistent with which of the following complexes?

A) [Co(NH₃)₄Cl₂]Cl
B) [Co(NH₃)₃Cl₃]
C) [Co(NH₃)₆]Cl₃
D) [Co(NH₃)₅Cl]Cl₂
E) none of these

Question 39

The complex ion [TiBr₄]^2- is tetrahedral. How many unpaired electrons are there in the complex?

A) 4
B) 1
C) 2
D) 3
E) 0

Question 40

A complex ion is a square planar complex. It has a d⁸ electron configuration. What is the most reasonable d orbital scheme for this complex?

A)
B)
C)
D)
E)

Question 41

Specify the number of unpaired electrons in [Ni(H₂O)₆]³⁺ (weak field).

A) 2
B) 0
C) 3
D) 1
E) 5

Question 42

How many unpaired electrons are found in Mn(CN)₆^3- (strong field)?

A) 2
B) 0
C) 4
D) 5
E) 1

Question 43

Which of the following crystal field diagrams is correct for Co(CN)₆^4-, where CN^- is a strong-field ligand?

A)
B)
C)
D)
E) none of these

Question 44

How many unpaired electrons are found in [CoCl₆]^3- (weak field)?

A) 2
B) 0
C) 1
D) 5
E) 4

Question 45

Specify the number of unpaired electrons in Co(en) ₃³⁺ (strong field).

A) 0
B) 1
C) 4
D) 5
E) 2

Question 46

How many unpaired electrons are found in Mn(NH₃)₄³⁺ (tetrahedral)?

A) 4
B) 5
C) 1
D) 0
E) 2

Question 47

How many unpaired electrons are found in [Co(CN)₄]^3- (square planar)?

A) 2
B) 0
C) 1
D) 4
E) 5

Question 48

How many unpaired electrons are found in Zn(H₂O)₆²⁺?

A) 4
B) 2
C) 5
D) 0
E) 1

Question 49

A certain complex ion has a distorted octahedral structure in which the ligands along the plus and minus z axes are compressed (pushed in closer to the central metal ion). The d orbital splitting diagram for this complex ion would be

A)
B)
C)
D)
E)

Question 50

How many unpaired electrons are found in NiBr₄^2- (tetrahedral)?

A) 0
B) 4
C) 1
D) 5
E) 2

Question 51

Which of the following is paramagnetic?

A) [Co(en)₆]³⁺ (strong field)
B) [Cu(en)₃]⁺
C) [Mn(CN)₆]^4- (strong field)
D) [Fe(en)₃]²⁺ (strong field)
E) [Zn(H₂O)₆]²⁺

Question 52

Specify the number of unpaired electrons in CoF₆^3- (weak field).

A) 4
B) 5
C) 1
D) 2
E) 0

Question 53

Specify the number of unpaired electrons in [CuCl₂]^-.

A) 3
B) 5
C) 4
D) 2
E) 0

Question 54

How many unpaired electrons are found in Fe(en)₃²⁺ (strong field)?

A) 5
B) 1
C) 2
D) 0
E) 4

Question 55

The complex ions of Zn²⁺ are all colorless. The most likely explanation for this is that

A) Zn²⁺ exhibits "d orbital" splittings in its complexes such that they absorb all wavelengths in the visible region.
B) because Zn²⁺ is a d¹⁰ ion, it does not absorb visible light even though the "d orbital" splittings are correct for absorbing visible wavelengths.
C) Zn²⁺ is paramagnetic.
D) Zn²⁺ is not a transition metal ion.
E) None of these explanations could be correct.

Question 56

Which of the following crystal field diagrams is correct for Mn(CN)₆^3- , where CN^- is a strong-field ligand?

A)
B)
C)
D)
E) none of these

Question 57

Specify the number of unpaired electrons in NiCl₄^2- (tetrahedral).

A) 0
B) 2
C) 4
D) 1
E) 5

Question 58

How many unpaired electrons are found in MnCl₄^2- (tetrahedral)?

A) 5
B) 0
C) 2
D) 1
E) 4

Question 59

How many unpaired electrons are there in the complex ion [Co(NO₃)₆]^4-? For this ion, the nitrate ligands produce a very strong crystal field.

A) 4
B) 5
C) 3
D) 2
E) 1

Question 60

Which of the following complexes would be diamagnetic (all electrons paired)?

A) Co(CN)₆]^3-
B) Mn(CN)₆]^4-
C) V(CN)₆]^3-
D) [Cr(CN)₆]^3-

Question 61

Calculate the total number of unpaired electrons in the following complex ions: [Zn(H₂O)₆]²⁺, [NiCN₄]^2- (square planar), [Co(NH₃)₆]³⁺ (strong field).

A) 0
B) 1
C) 3
D) 2
E) 4

Question 62

This molecule is toxic because it has about 200 times the affinity for the Fe²⁺ in hemoglobin that oxygen does, causing asphyxiation if enough of it is present in the air.

A) NH₃
B) CO₂
C) CO
D) CN^-
E) CH₄

Question 63

Here are some crystal field representations of d electrons in an octahedral field: Choose the representation that fits the transition metal atom in the following species.
[Co(NH₃)₄Br₂]⁺

A)
B)
C)
D)
E)

Question 64

How many unpaired electrons are there in Ir(Br)₆^4-? (Br^- is a weak-field ligand.)

A) 2
B) 4
C) 3
D) 0
E) 1

Question 65

Choose the most likely pattern for the crystal field diagram for the complex trans-[Ni(NH₃)₂(CN)₄]^2-, where CN^- produces a much stronger crystal field than does NH₃.

A)
B)
C)
D)
E)

Question 66

Carboxyhemoglobin is formed when __________ prevents the normal uptake of oxygen in the blood.

A) CN^-
B) CH₄
C) CO₂
D) NH₃
E) CO

Question 67

Which has the greater number of unpaired electrons?
I. square planar Ni(CN)₄^2-
II. tetrahedral FeCl₄^-

A) I
B) II
C) Neither I nor II has any unpaired electrons.
D) More information is needed.
E) Both I and II have the same (nonzero) number of unpaired electrons.

Question 68

A d⁶ ion (Fe²⁺) is complexed with six strong-field ligands (for example, SCN^-). What is the number of unpaired electrons in this complex?

A) 3
B) 2
C) 0
D) 1
E) 4

Question 69

Specify the number of unpaired electrons in [Mn(H₂O)₄]²⁺ (tetrahedral).

A) 2
B) 1
C) 4
D) 5
E) 0

Question 70

Which of the following statements is true about the octahedral complexes of Ni²⁺?

A) Both strong- and weak-field complexes are paramagnetic.
B) The strong-field complex is paramagnetic and the weak-field complex is diamagnetic.
C) Both strong- and weak-field complexes are diamagnetic.
D) The strong-field complex is diamagnetic and the weak-field complex is paramagnetic.

Question 71

In _________, the isomers contain the same atoms, but one or more bonds differ.

Question 72

In _________, all bonds are the same, but the spatial arrangements of atoms are different.

Question 73

The complex ion Fe(CN)₆^4- (no unpaired electrons) is classified as

A) There is no way to tell.
B) strong field.
C) weak field.

Question 74

According to crystal field theory, how many unpaired electrons are present in the complex ion [Zn(H₂O)₆]²⁺?

A) 2
B) 3
C) 4
D) 1
E) 0

Question 75

The complex ion Co(NH₃)₆²⁺ (three unpaired electrons) is classified as

A) There is no way to tell.
B) strong field.
C) weak field.

Question 76

Oxygen is stored in mammalian tissue in which type of molecule?

A) chlorophyll
B) cytochrome
C) hemoglobin
D) prophyrin
E) myoglobin

Question 77

Here are some crystal field representations of d electrons in an octahedral field: Choose the representation that fits the transition metal atom in the following species.
Fe(OH₂)₆³⁺ (assume weak field)

A)
B)
C)
D)
E)

Question 78

Which of the following transition metals is a component of vitamin B₁₂?

A) chromium
B) zinc
C) copper
D) manganese
E) cobalt

Question 79

Which of the following ligands are capable of linkage isomerism?

Question 80

The complex ion Ni(NH₃)₆²⁺ (two unpaired electrons) is classified as

A) There is no way to tell.
B) strong field.
C) weak field.