Chem 124 Ch.23(3-4)

Question 1

Two coordination compounds that have the same ligands arranged differently in space around the central metal ion, but are not mirror images of one another, are called____isomers. If the identical ligands are next to each other, the isomer is described as____ while the isomer with identical ligands across from each other is the____ isomer.

Answer 1

geometric/cis-trans; cis; trans

Question 2

What is the difference btwn cis and trans geometric isomers?

Answer 2

• Cis has compounds or molecules next to each other (w/ the middle being across from each other) w/ different dashes
• Trans has compounds or molecules across from each other with diff dashes (the metal cation is inbtwn).

Question 3

If two compounds are mirror images of one another, but are not superimposable (lay over one another), they are called____ isomers or enantiomers. These isomers have____ physical properties except for the direction in which each rotates the plane of polarized light.

Answer 3

optical; identical

Question 4

An object appears to be red. What can correctly explain this observation?

• absorbs only blue light
• absorbs only green light
• absorbs only red light
• absorbs all wavelengths of light except red.
• absorbs all colors that are similar to red.

Answer 4

• absorbs all wavelengths of light except red.
• absorbs only green light
  Reason: Green is its complementary color-> if it absorbs green the it will show as red

Question 5

What correctly describe geometric isomers of coordination compounds?

• A coordination compound might have geometric isomers of the ligands can be arranged differently in space relative to the central metal ion.
• The isomer that has identical ligands adjacent to each other is called the cis isomer.
• A coordination compound will have geometric isomers if all possible arrangements of the ligands give the same compound.
• Geometric isomers are diff compounds and have diff physical prop.
• The isomer that has diff ligands across from each other is called the trans isomer

Answer 5

• A coordination compound might have geometric isomers of the ligands can be arranged differently in space relative to the central metal ion.
• The isomer that has identical ligands adjacent to each other is called the cis isomer.
• Geometric isomers are diff compounds and have diff physical prop.

Question 6

Which of the following complex ions can exist as a pair of cis-trans isomers? Select all that apply.

• [Pd(NH3)3Cl]+
• [Pd(CN)2(OH)2]2–
• [Pt(NH3)4Br2]2+
• [Fe(CN)6]3–

Answer 6

• [Pd(CN)2(OH)2]2–
  Reason: A complex ion of Pd with a coordination number of 4 is square planar. The CN ligands in this ion could be adjacent to each other or across from each other, so [Pd(CN)2(OH)2]2– exists as a pair of cis-trans isomers.
• [Pt(NH3)4Br2]2+
  Reason: Pt with a coordination number of 6 is octahedral. [Pt(NH3)4Br2]2+ exists as a pair of cis-trans isomers because the 2 Br ligands could either be next to each other or across from each other.

Question 7

Match the color given w/ the color and wavelength of light absorbed
Blue->
Red->
Violet->

• Yellow-green:570nm
• Orange:600nm
• Blue-green:490 nm

Answer 7

Blue-> Orange:600nm
Red-> Blue-green:490 nm
Violet-> Yellow-green:570nm

Question 8

What statements correctly describe a pair of optical isomers?

• Optical isomers rotate plane polarized light in opposite directions.
• The mirror image of any compound is called it’s optical isomer.
  -Optical isomers exist for all octahedral coordination complexes.
• Optical isomers have identical melting and boiling points.
• Optical isomers are mirror-image compounds that cant be superimposed.

Answer 8

• Optical isomers have identical melting and boiling points.
• Optical isomers rotate plane polarized light in opposite directions.
• Optical isomers are mirror-image compounds that cant be superimposed.

Question 9

An object has a particular color if it ____ light of that color, or if it absorbs only ____ color.

• Reflects; supplementary
• Reflects; complementary
• absorbs; supplementary
• absorbs; complementary

Answer 9

• Reflects; complementary

Question 10

What is the color of a complex ion that absorbs light primarily in the 450 nm range?

• blue
• orange
• white
• black

Answer 10

• orange

Question 11

What statements correctly describe the crystal field model as it applies to the formation of an octahedral complex?

• As ligands approach the metal ion, there is repulsion between the ligand electrons and the metal ion electrons.
• After bonding, the d orbitals of the metal ion are split into 2 groups of different energies.
• Before bonding the d orbitals of the metal ion are identical in energy and shape.
• The ligands interact equally with all five d orbitals of the metal ion.
• Ligand-metal ion repulsions are not the same for all the d orbitals of the metal ion.

Answer 11

• As ligands approach the metal ion, there is repulsion between the ligand electrons and the metal ion electrons.
• Ligand-metal ion repulsions are not the same for all the d orbitals of the metal ion.
• After bonding, the d orbitals of the metal ion are split into 2 groups of different energies.

Question 12

When a metal cation forms an octahedral complex the ligands approach directly along the x, y, and z axes. The two d orbitals with lobes along the axes will experience a _____ repulsion than the three d orbitals with lobes between the axes. The d orbitals will be split into two groups; the higher energy group has _____ orbitals and the lower energy group has _____ orbitals.

• lower; three; two
• lower; two; three
• greater; two; three
• greater; three; two

Answer 12

• greater; two; three

Question 13

The splitting of d-orbital energies into two groups by the interaction of a metal ion with a group of ligands is called the crystal field____, and the energy difference between the two groups of d orbitals is the crystal field____ energy of that field.

Answer 13

effect; splitting

Question 14

Match each type of ligand w/ the correct description of the crystal field.
strong-field ligands->
weak-field ligands ->

• smaller crystal field splitting energy
• larger crystal field splitting energy

Answer 14

strong-field ligands-> larger crystal field splitting energy
weak-field ligands ->smaller crystal field splitting energy

Question 15

Why do the ligands cause splitting of the metal ion d-orbital energies when a complex ion is formed?

• the 5 d orbitals have diff orientations and are not all repelled equally by the approaching ligands.
• The 5 d orbitals repel each other as well as the approaching ligands.
• the d orbitals are not all the same energy before bonding occurs.

Answer 15

• the 5 d orbitals have diff orientations and are not all repelled equally by the approaching ligands.

Question 16

When a coordination complex absorbs light, a d electron moves from a____energy d orbital to a ____energy one. The wavelength of light absorbed, and hence the color observed, depends on the energy____ between the orbitals, which is equal to the crystal field____ energy (Δ).

Answer 16

low;high,gap;splitting

Question 17

What statements describe the arrangement of the d orbitals in a metal cation after the formation of an octahedral complex?

• “There will be” 3 higher energy d orbitals designated eg orbitals.
• ”..” 2 higher energy d orbitals designated eg orbitals.
• “…” 3 lower energy d orbitals designated t2g orbitals.
• All 5 d orbitals will have the same splitting an thus will have the same energy.

Answer 17

• ”..” 2 higher energy d orbitals designated eg orbitals.
• “…” 3 lower energy d orbitals designated t2g orbitals.

Question 18

How do you know (given the complex ion) will appear a certain color?

Answer 18

Orange: if it has a larger Δ

Question 19

Which of the following options correctly describe the magnetic properties of transition metal complexes? Select all that apply.

• A strong-field ligand has a large Δ, leading to more unpaired electrons.
• A weak-field ligand will have the same number of unpaired electrons as the free ion.
• A low-spin complex contains fewer unpaired electrons than a high-spin complex.
• The number of unpaired electrons depends both on the metal ion and on the ligands.
• A strong-field ligand forms a high-spin complex.

Answer 19

• A weak-field ligand will have the same number of unpaired electrons as the free ion.
• A low-spin complex contains fewer unpaired electrons than a high-spin complex.
• The number of unpaired electrons depends both on the metal ion and on the ligands.

Question 20

Which of the following statements correctly describe the factors affecting the color of a particular coordination complex? Select all that apply.

• The color depends only on the nature of the ligands.
• The splitting energy of the complex determines the wavelengths of light absorbed and hence the color.
• For a given metal ion, the color depends on the ligand.
• For a given ligand, the color depends on the oxidation state of the metal ion.

Answer 20

• For a given ligand, the color depends on the oxidation state of the metal ion.
• The splitting energy of the complex determines the wavelengths of light absorbed and hence the color.
• For a given metal ion, the color depends on the ligand.

Question 21

Which of the following complex ions will have only one unpaired electron? Select all that apply.

• [MnCl6]4–
• [Mn(CO)6]2+
• [Mn(CN)6]4–
• [Mn(en)6]2+
• [Mn(H2O)5Cl]+

Answer 21

• [Mn(CO)6]2+
• [Mn(CN)6]4–
• [Mn(en)6]2+

Question 22

The difference in splitting of d-orbital energies for ______ complexes is simply the reverse of that for the ______ complexes.

• square-planar; octahedral
• square-planar; square-pyramidal
• tetrahedral; octahedral
• tetrahedral; square-planar

Answer 22

• tetrahedral; octahedral

Question 23

Electrons in the d orbitals of a complex ion may enter the higher energy d orbitals once the lower energy d orbitals are half filled if the value of Δ is _____. Electrons will completely fill the lower energy d orbitals before entering the higher energy d orbitals if the value of Δ is _____.

• small;large
• large;small

Answer 23

• small;large

Question 24

Match each complex ion w/ the correct # of unpaired e-.
Mn(CN)64– ->
Co(en)33+ ->
FeCl42– ->
Co(H2O)62+ ->

• 0 unpaired e-
• 1 unpaired e-
• 4 unpaired e-
• 3 unpaired e-

Answer 24

Mn(CN)64– -> 1
Co(en)33+ -> 0
FeCl42– -> 4
Co(H2O)62+ -> 3

Question 25

Which of the following statements correctly describe the differences between octahedral, square planar, and tetrahedral complexes? Select all that apply.

• Square planar complexes tend to be low-spin complexes.
• Tetrahedral complexes have smaller splitting energies than octahedral complexes.
• Square planar complexes are usually diamagnetic.
• A square planar complex has 2 lower energy d orbitals and three higher energy d orbitals.
• Tetrahedral complexes are all low-spin complexes.

Answer 25

• Square planar complexes are usually diamagnetic.
• Square planar complexes tend to be low-spin complexes.
• Tetrahedral complexes have smaller splitting energies than octahedral complexes.