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100問 • 1年前

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Which of the following is an example of coordination isomerism?

[Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6]

Which of the following complexes can exhibit both geometrical and optical isomerism?

[Co(en)3]3+

Which pair of complexes demonstrates coordination isomerism?

[Ni(NH3)6]C12 and [NiCl2(NH3)4]

The number of geometrical isomers possible for the octahedral complex [Co(NH3)3C13] is:

Which of the following complexes can exhibit linkage isomerism?

[Co(NH3)5(NO2)]C12

Which of the following complexes can exhibit coordination tautomerism?

[Pt(NH3)2(OH)(NO)]+

Which of the following is an example of structural isomerism in polynuclear complexes?

[Co(NH3)5(NO2)]C12 and [Co(NH3)5(ONO)]C12

Which of the following geometrical isomers is more stable for the square planar complex [PtCl2(NH3)2]?

Trans-isomer

Which spectroscopic technique is most commonly used to distinguish between cis and trans isomers of square planar complexes like [PtCl2(NH3)2]?

UV-Vis Spectroscopy

Which of the following complexes will show significant Jahn-Teller distortion and isomer-dependent reactivity?

[Mn(NH3)6]2+

Which of the following statements about geometric isomerism in square planar complexes is false?

All square planar complexes exhibit geometric isomerism.

What happens to the Fe(III) ion in [Fe(sal2-trien)] upon heating, leading to temperature-induced isomerism?

Transition from a high-spin to a low-spin state

Which of the following pairs of compounds are linkage isomers?

[Cr(H2O)5CI]C12 and [Cr(H2O)4C12]Cl

Which of the following best describes coordination tautomerism?

Isomerism due to proton transfer within a ligand in the coordination sphere.

In the complex [Fe2(CO)9], which of the following describes a structural isomer?

Conversion of terminal carbonyls to bridging carbonyls

In octahedral complexes, the cis-isomer is often more reactive than the trans-isomer. Which electronic effect explains this phenomenon?

Trans effect

A complex [Co(NH3)5(NO2)]C12 shows two IR bands at 1320 cm-1 and 1470 cm-1. What does this indicate about the coordination mode of the NO2- ligand?

Nitrito coordination through oxygen

In tetragonal Jahn-Teller distortion, which structural feature is typically observed?

Compression of axial bonds and elongation of equatorial bonds

Which type of isomerism is exhibited by the complex [Co(NH), Cl] when dissolved in water?

Ionization isomerism

Which of the following correctly describes temperature-induced isomerism in nitro/nitrito complexes?

The isomerism results from a change in ligand geometry.

In an octahedral complex, which set of d-orbitals experiences the maximum crystal field splitting energy (Ao) due to ligand interactions?

dz2,dx2-y2

Crystal Field Theory fails to explain why CuC14]2-is distorted into a tetragonal geometry (Jahn-Teller effect). Which principle provides the most accurate explanation for this distortion?

Symmetry-breaking to lower electronic energy

Which statement correctly describes how Ligand Field Theory (LFT) extends Crystal Field Theory (CFT)?

LFT incorporates both electrostatic and covalent interactions between the metal and ligands.

Which physical property of a coordination complex is most directly affected by Jahn-Teller distortion?

Bond lengths within the coordination sphere

Which of the following ligands is expected to cause the highest crystal field splitting energy (A) in an octahedral complex?

CN-

Which factor most strongly influences the energy of charge transfer transitions in coordination complexes?

The relative energy gap between the metal orbitals and ligand orbitals

In the Angular Overlap Model (AOM), which of the following metal-ligand interactions contributes the most to the stabilization of dz2 orbitals in a square planar complex?

π-backbonding interactions along the z-axis.

Which of the following factors increases the extent of a-backbonding in a metal carbonyl complex?

A low-lying d-orbital energy on the metal center.

The crystal field stabilization energy (CFSE) for a d4 low-spin octahedral complex in the presence of a strong field ligand is:

-1.6delta0 +P

Crystal Field Theory predicts the splitting of d-orbitals in a ligand field but does not fully explain the order of ligand strength in the spectrochemical series. Which of the following contributes most to the order?

π-acceptor or π-donor interactions

In Ligand Field Theory, the bonding in [Fe(CN)6]4- is described as a combination of 6-donation and z-backbonding. Which of the following is the primary consequence of r-backbonding in this complex?

Increase in Ao due to ligand x-acceptor ability.

For a low-spin d7 octahedral complex, what type of Jahn-Teller distortion is expected based on Ligand Field Theory?

Axial compression due to unequal eg orbital occupancy.

The relatively low field strength of F- in the spectrochemical series is primarily attributed to:

Poor overlap between F- orbitals and metal d-orbitals.

Why are many charge transfer bands more intense than d-d transitions in the UV- Vis spectra of coordination complexes?

Charge transfer bands involve fully allowed transitions between orbitals of different symmetry.

Which orbital in a tetrahedral complex experiences the least stabilization based on the Angular Overlap Model?

dx2-y2

Why does [Cp2TiC12] (where Cp cyclopentadienyl) exhibit stability despite the presence of reactive metal-ligand bonds?

The 15 bonding of Cp ligands provides aromatic stabilization and strong a-donation.

Which bonding theory is best suited to predict the magnetic properties of transition metal complexes and why?

Molecular Orbital Theory (MOT) because it considers both metal and ligand orbitals in detail.

Which relativistic effect primarily influences the stability and reactivity of 5d transition metal complexes?

Contraction of s and p orbitals and relativistic stabilization of d-orbitals.

Which reaction mechanism is involved in the racemization of a chiral octahedral complex such as [Co(en)3]3+?

Bailar twist or Ray-Dutt mechanism.

Which of the following complexes is most likely to undergo an inner-sphere electron transfer mechanism?

[Co(NH3)5C1]2+ and [Cr(H2O)6]2+

Which of the following metal complexes is expected to be the most labile in aqueous solution?

[Cu(H2O)6]2+

Which of the following ligands is most commonly associated with linkage isomerism?

NO2-

Consider the following reaction: [PtC14]2-+NH3 [PtC13(NH3)]-+CI- If the rate of the reaction increases significantly upon replacing one Cl- ligand with Br-, what is the most likely explanation?

Br-has a stronger trans effect than Cl-.

For the complex [Co(NH3)6]3+, the observed absorption occurs at a wavelength of 475 nm. Using the spectrochemical series, which ligand substitution would shift the absorption to a shorter wavelength?

NH3 replaced by CN-.

Why does [Fe(CN)6]3- exhibit lower spin magnetic behavior compared to [FeF6]3-?

B. The stronger π-acceptor ability of CN- compared to F-.

Why do heavy transition metals such as gold and platinum often form stronger covalent bonds compared to their lighter counterparts?

Relativistic effects stabilize the metal's valence orbitals, enhancing overlap with ligand orbitals.

Which of the following is a characteristic feature of inner-sphere electron transfer reactions in coordination chemistry?

Electron transfer occurs through a bridging ligand shared between donor and acceptor.

Which of the following factors significantly enhances the rate of outer-sphere electron transfer in coordination chemistry?

Small energy gap between the donor and acceptor redox states.

Which property distinguishes labile complexes from inert ones in terms of their reaction mechanisms?

exhibit fast ligand substitution, whereas inert ones have a higher activation energy for substitution.

What drives the conversion between nitro (-NO2) and nitrito (ONO) linkage isomers in coordination compounds?

Changes in electronic or steric factors in the coordination sphere.

A substitution reaction involving [Co(NH3)5C1]2+ in water follows the rate law: Rate = k[Co(NH3)5C12+], Which of the following mechanisms is consistent with this rate law?

Dissociative mechanism with Cl-leaving first.

The complex [Fe(H2O)6]2+ absorbs light in the green region of the spectrum. Replacing H2O with NH3 changes the color to yellow. What is the best explanation for this observation?

NH3 is a stronger field ligand than H2O, increasing A.

The complex [Cu(H2O)6]2+ exhibits a distorted octahedral geometry and a characteristic absorption band in the visible region. What causes the distortion?

The Jahn-Teller effect in the d9 electronic configuration.

For a d3 complex in an octahedral field, the Tanabe-Sugano diagram shows a transition labeled as 4A24T2. If the absorption maximum for this transition occurs at 20,000 cm-1, what is the approximate crystal field splitting energy (Ao) for this complex?

15,000 cm-1

In the electronic spectrum of [Mn(H2O)6]3+, why is no significant Jahn-Teller distortion observed?

The electronic configuration t3/2g el/g minimizes distortion effects.

Using the Tanabe-Sugano diagram for a d5 high-spin octahedral complex, predict the number of spin-allowed transitions expected in the electronic spectrum.

The complex [Co(NH3)6]3+ appears yellow in color. If the absorption maximum is measured at 400 nm, which region of the electromagnetic spectrum is primarily responsible for the absorption?

Visible (green region)

The UV-Vis spectrum of [Cr(H2O)6]3+ shows three absorption bands at 17,400 cm-1, 24,000 cm-1, and 37,000 cm-1. What do these bands correspond to?

Spin-allowed d-d transitions.

For a d2 octahedral complex, the energies of the electronic transitions 3T1 3T2 and 3T1→3A2 are observed to be 12,000 cm-1 and 18,000 cm-1, respectively. Calculate the Racah parameter B.

600 cm-1

The UV-Vis spectrum of [Ni(H2O)6]2+ (octahedral complex) shows absorption bands at 8,500 cm-1, 14,300 cm-1, and 25,000 cm-1. Calculate the approximate value of A (ligand field splitting energy) for this complex.

14,300 cm-1

Which of the following electronic transitions in a coordination compound is typically forbidden by Laporte's selection rule for centrosymmetric complexes?

d→d

A solution of [Cr(H2O)6]3+ is purple due to an absorption band at 575 nm. What is the likely cause of this absorption band?

Spin-allowed d-d transition.

In the IR spectrum of a coordination complex, two distinct C=O stretching frequencies are observed. What does this indicate about the complex?

Asymmetrical binding of CO ligands to the metal center.

If the Racah parameter B for a free ion is 1,200 cm-1 and decreases to 900 cm-1 upon coordination to ligands, what does this change indicate?

Decreased inter-electronic repulsion in the complex.

The complex [Fe(CN)6]3- (low-spin d5) has a ligand field splitting energy (A)of approximately 35,000 cm-1. What is the primary reason for the high value of A in this complex?

The strong field nature of CN-ligands.

Which type of transition in coordination complexes is associated with intense absorption bands in the UV-Vis spectrum?

Charge transfer transitions

Which statement best explains the photochemical behavior of a coordination compound undergoing metal-to-ligand charge transfer (MLCT)?

The excited state involves delocalization of electron density onto the ligand.

In a photoredox reaction involving a Ru(II)-polypyridyl complex, which step is most critical for the formation of a reactive species?

Intersystem crossing to the triplet MLCT state.

Which of the following statements correctly describes the role of a coordination complex in photochemical water-splitting systems for solar energy conversion?

The coordination complex absorbs light, undergoes photoexcitation, and mediates electron transfer to generate oxygen and hydrogen.

A coordination complex absorbs light at 450 nm in a photochemical experiment. The molar extinction coefficient (2) of the complex at this wavelength is 5000M-1 cm-1. A solution of the complex has an absorbance of 0.5 in a 1 cm pathlength cuvette. What is the molarity of the complex in the solution?

1.0×10-4 M

A luminescent Ru(II) complex has an emission maximum at 600 nm with a fluorescence quantum yield (Of) of 0.25. The lifetime (r) of the excited state is measured as 200 ns. What is the radiative decay rate constant (kr) of the excited state?

1.25×106 s-1

A coordination compound shows a strong absorption band in the UV-Vis spectrum at 350 nm due to ligand-to-metal charge transfer (LMCT). What feature of the ligand is most likely responsible for this transition?

The ligand has a low-energy lone pair capable of donating electrons.

Which of the following factors increases the quantum yield of photoredox reactions in coordination compounds?

A long-lived excited state with strong charge-transfer character.

A Ru(II) polypyridyl complex is often used as a photocatalyst in solar energy conversion due to its long-lived excited state. Which feature of the complex primarily contributes to this property?

Strong π-acceptor properties of the polypyridyl ligands.

A photochemical quantum yield (Ф) experiment is conducted on a coordination complex to study its photoinduced electron transfer. The system absorbs 2.5mJ of light at 500 nm, and 4.0×10-8 mol of electrons are produced. What is the quantum yield of the reaction? (Planck's constant, h = 6.626×10-34 J; speed of light, c = 3.0×108 m/s)

0.48

A luminescent coordination complex is used as a pH sensor. Its emission intensity decreases linearly from 100% to 20% as the pH increases from 5 to 9. What is the emission intensity at pH 7?

60%

Which of the following is an example of a topotactic solid-state reaction?

The intercalation of lithium ions into layered TiS, during battery charging.

In a solid-state reaction, A2B3 decomposes into 2A+B2. If 10 g of A2B3 (molar mass 200 g/mol) is decomposed completely, what is the total number of moles of gas produced at standard temperature and pressure (STP)?

0.10 mol

Which solid-state reaction is critical for the production of high-temperature superconductors?

The synthesis of YBa Cu Ox by solid-state reaction of oxides and carbonates.

A synthesized solid-state compound shows an XRD peak at 20-30-. If the wavelength of X-rays used is λ=1.54064°, what is the interplanar spacing (d) for this peak? (assume n=1.)

3.08 Å

A solid-state reaction for the formation of BaTiO3 from BaCO3 and TiO2 involves a mass loss of CO₂. If 1 mole of BaCO3 (molar mass = 197 g/mol) reacts completely, what is the mass of CO, released? (Molar mass of CO, = 44 g/mol)

88 g

A solid-state product synthesized at high temperature is suspected to contain impurities. Which characterization method is most appropriate for identifying the chemical composition of the product?

Energy Dispersive X-ray Spectroscopy (EDX)

Which of the following is a primary advantage of solid-state reactions performed using mechanochemical synthesis?

Enhanced reaction kinetics due to increased surface area and defect formation.

A solid-state reaction involving ZnO and Al2O3 to form spinel ZnA1204 is conducted at 1200°C. If 5.0 g of ZnO (molar mass 81.4 g/mol) is used, what is the minimum mass of Al2O3 (molar mass = 102 g/mol) required for the reaction? (The reaction stoichiometry is ZnO+Al2O3 → ZnAl2O4.)

2.50 g

A radioactive isotope has a half-life of 5 years. If you start with a 100 g sample, how much of the isotope remains after 15 years?

25 g

A sample of Ra-226 has an initial activity of 400Bq. If the half-life of Ra-226 is 1600 years, what will the activity be after 4800 years? (where t is the elapsed time and T is the half-life.)

100 Bq

Which of the following isotopes is part of the uranium radioactive decay series?

Ra-226

A patient undergoing radiation therapy receives a total dose of 60Gy over a tumor mass of 2.0kg. What is the total energy absorbed by the tumor in joules? Note: 1Gy = 1 J/Kg

120 J

Which of the following coordination complexes is most likely to undergo a photoinduced ligand substitution reaction?

[Fe(CO)5]

A Tb3+-based complex absorbs a photon at 488 nm via an antenna ligand. If the quantum yield for luminescence is 0.60, and the energy transfer efficiency from the ligand to Tb3+ is 75%, what fraction of the absorbed photon energy is emitted as luminescence?

0.55

A radioactive isotope decays into a stable isotope through a series of steps. If the mass ratio of the parent isotope to the daughter isotope in a sample is 1:7, how many half-lives have elapsed?

Which of the following effects is most likely a result of low-dose, long-term radiation exposure?

DNA mutations leading to cancer

A [Ru(bpy)3]2+ complex undergoes a photoinduced ligand substitution reaction, replacing one bpy ligand with Cl-. If the activation energy for the ground-state substitution is 150 kJ/mol and the energy of the absorbed photon is 200 kJ/mol, what is the effective activation energy for the photoinduced process?

50 kJ/mol

Lanthanide ions are commonly used in photochemistry due to their unique electronic properties. Which of the following characteristics makes Eu3+ and Tb3+ ideal for luminescence applications?

Their strong f-f transitions, which are shielded from the environment

Why are Ru(II) polypyridyl complexes widely used in dye-sensitized solar cells (DSSCs)?

They have strong metal-to-ligand charge transfer (MLCT) absorption bands.

Which of the following nuclei is expected to be most stable based on the neutron-to- proton (N/Z) ratio and nuclear binding energy considerations?

Fe 56/26

Calculate the nuclear binding energy of O 16/8, which has an atomic mass of 15.9949u. The mass of a proton is 1.0078u, and the mass of a neutron is 1.0087u. Use lu = 931.5MeV.

128.7 MeV

A coordination complex used in a DSSC absorbs light at 500 nm and injects an electron into TiO2 with 80% efficiency. If the incident light intensity is 1000W/m2, what is the power available for electron injection per square meter? (Planck's constant h=6.626×10-34 J, speed of light c=3.00×108 m/s.)

320 W/m2

Calculate the N/Z ratio for U 235/92. Based on the N/Z ratio, determine if the nucleus is likely to be stable or radioactive.

1.52, radioactive

100

If a nucleus undergoes fission, releasing energy, what can be inferred about the nuclear binding energy of the resulting fragments compared to the original nucleus?

The fragments have a higher binding energy per nucleon.

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