PHOTOCHEMISTRY AND MOLECULAR SYMMETRY MCQs

PHOTOCHEMISTRY AND MOLECULAR SYMMETRY MCQs

One mole of photon is called _____ .

  1. Quantum
  2. Energy Packet
  3. Einstein
  4. None of A, B, and C

Einstein

The emission of light in a biological reaction is called ___.

  1. Fluorescence
  2. Phosphorescence
  3. Chemiluminescence
  4. Bioluminescence

Bioluminescence

“Only those radiations which are absorbed by the system can bring about chemical change”. This is a statement of the

A Beer-Lambert law

  1. Photochemical equivalence law
  2. Einstein law
  3. Grotthus-Draper law

Grotthus-Draper law

____ is the glow of yellow phosphorous as a result of slow oxidation in air.

  1. Photolysis
  2. Luminescence
  3. Bioluminescence
  4. Chemiluminescene

Chemiluminescene

The spin multiplicity of the electronic state is equal to

  1. S+1
  2. 2S + 2
  3. 2S – 2
  4. 2S + 1

2S + 1

Reactions in which molecules absorbing light do not themselves react but induce other molecules to react are called

  1. Chain reactions
  2. Free radical reactions
  3. Reversible reactions
  4. Photosensitized reactions

Photosensitized reactions

A molecule returns from the excited singlet state to the ground singlet state with emission of light. This process is called _____ .

  1. Phosphorescence
  2. Scattering
  3. Fluorescence
  4. Chemiluminescence

Fluorescence

Which statement is not true with respect to photochemical reactions?

  1. Temperature has significant effect on rate of these reactions
  2. Free energy of these reactions may be positive or negative
  3. Light intensity affects these reactions
  4. These take place in the presence of light

Temperature has significant effect on rate of these reactions

Which statement is not related with high quantum yield reasons?

  1. The primary photochemical process may be reversed
  2. The active molecules may collide with other molecules and activate these molecules
  3. The reaction may be exothermic and heat evolve may activate other molecules
  4. Formation of reactive intermediates which may act as catalyst

The primary photochemical process may be reversed

According to “The Lambert-Beer law” , ______

  1. Transmission is directly proportional to path length
  2. Transmission is directly proportional to concentration
  3. Absorbance is directly proportional to concentration & path length
  4. Absorbance is inversely proportional to transmission

Absorbance is directly proportional to concentration & path length

A molecule goes from the excited singlet to the triplet state without emitting light. The process is called _____ .

  1. Inter-system crossing
  2. Phosphorescence
  3. Internal conversion
  4. Fluorescence

Inter-system crossing

When a transition occurs between states the same multiplicity without emitting light, the process is called

  1. Fluorescence
  2. Quenching
  3. Intersystem crossing
  4. Internal conversion

Internal conversion

A molecule returns from the first excited triplet sate to the ground singlet state. The light emitted is called _____ .

  1. Inter-system crossing
  2. Phosphorescence
  3. Fluorescence
  4. Quenching

Phosphorescence

The quantum yield of a photochemical reaction is

  1. Can have any value 0 depending on the reaction
  2. Forever equal to unity
  3. Forever greater than unity
  4. Forever less than unity

Can have any value 0 depending on the reaction

Which reaction does not take place with light radiation?

  1. Double displacement
  2. Reduction
  3. Polymerization
  4. Oxidation

Double displacement

Which radiations are photo chemically active?

  1. Micro waves
  2. Radio waves
  3. Ultraviolet
  4. Infrared

Ultraviolet

The wavelength of fluorescent light () is related to the wavelength of absorbed light (b) by

  1. λf > λab
  2. λf > λab
  3. λf λab
  4. λf < λab

λf > λab

The value of an Einstein

  1. Is independent of wavelength
  2. Depends on the temperature of the absorbing system
  3. Increases with increase in wavelength
  4. Decreases with increase in wavelength

Decreases with increase in wavelength

Ethylene belongs to

  1. C2v group
  2. D∞h group
  3. C2v group
  4. D2v group

D2v group

Which molecules have center of symmetry?

  1. H2O
  2. HCI
  3. H2SO4
  4. CO2

CO2

According to the Grotthus-Draper law

  1. Only absorbed light is effective in producing photochemical changes
  2. Only light between certain wavelengths is effective in photochemical changes
  3. The light absorbed is proportional to its intensity
  4. Light is effective only for photochemical reactions in solution.

Only absorbed light is effective in producing photochemical changes

Which molecules belongs to C3V point group?

  1. NH3
  2. H₂S
  3. BF3
  4. H₂O

NH3

The branch of chemistry dealing with the study of reactions in the UV-visible region of the spectrum is called _____ .

  1. Kinetics
  2. Cryoscopy
  3. Surface chemistry
  4. Photochemistry

Photochemistry

A line, a point or a plane about which a symmetry operation is performed, is called _____ .

  1. Symmetry
  2. Symmetry operation
  3. Reflection
  4. Inversion element

Symmetry

Which items is not symmetry element?

  1. Optical activity
  2. Inversion center
  3. Improper rotation
  4. Plane of symmetry

Optical activity

What is the reverse of a photochemical reaction?

  1. Phosphorescence
  2. Photosensitization
  3. Fluorescence
  4. Chemiluminescence

Chemiluminescence

Which symmetry element leaves the molecule or an object unchanged?

  1. Identity
  2. Improper rotation
  3. Inversion axis
  4. Proper rotation

Identity

In proper rotation (Cn), an object is rotated through an angle of

  1. π /n radians
  2. 4π/n radians
  3. 3π/n radians
  4. 2π/n radians

2π/n radians

Which molecules possess horizontal mirror plane?

  1. PF3
  2. Water
  3. Ammonia
  4. H2S

PF3

What is the point group of CO2?

  1. D6h
  2. C4v
  3. C6v
  4. D2h

D6h

A photosensitizer is a substance that

  1. Initiates a photochemical reaction
  2. Decreases the speed of a chemical reaction
  3. Stops the photochemical reaction
  4. Increases the speed of a chemical reaction

Initiates a photochemical reaction

The extinction coefficient has the units

  1. cm³ mol-1
  2. cm² mol-1
  3. mol cm–²
  4. mol cm-3

cm² mol-1

Which techniques is helpful and used to study photochemical processes?

  1. Flash photolysis
  2. Dilatometry
  3. Viscometry
  4. Polarimetry

Flash photolysis

CO belongs to which group?

  1. C2v
  2. D2h
  3. D∞h
  4. C∞v

C∞v

How many planes of symmetry are present in benzene?

  1. 6 planes
  2. 3 planes
  3. 5 planes
  4. 1 plane

6 planes

PF5 belongs to which point group

  1. D2h
  2. D4h
  3. D5h
  4. D3h

D3h

The point group of XeOF4 is

  1. C6v
  2. D2h
  3. D4h
  4. C4v

C4v

What is the point group of BF3?

  1. D3h
  2. C4v
  3. C3v
  4. D2h

D3h

Linear molecules have ____ axis of rotation

  1. C∞
  2. C2
  3. C3
  4. C1

C∞

In C-axis of rotation, an object is rotated through an angle of

  1. 90°
  2. 180°
  3. 100°
  4. 120°

90°

What is the point group of benzene?

  1. D6h
  2. C4v
  3. C6v
  4. D2h

D6h

What is the point group of SF6?

  1. C6v
  2. C4v
  3. Tetrahedral
  4. Octahedral

Octahedral

Which is a non-radioactive relaxation process?

  1. Internal conversion
  2. Intersystem crossing
  3. Vibrational relaxation
  4. All of A, B, and C

All of A, B, and C

Which molecules have rotation-reflection axis?

  1. Methane
  2. Allenes
  3. Staggered ethene
  4. All of A, B, and C

All of A, B, and C

Which molecules belong to special point group D∞h?

  1. CO2
  2. H2
  3. Cl2
  4. All of A, B, and C

All of A, B, and C

In a photochemical reaction

  1. ΔF is positive
  2. ΔF is negative.
  3. ΔF is 0
  4. None of A, B, and C

ΔF is positive

Which statement is not true with respect to group theory?

  1. Each group element has no reciprocal
  2. An element combines with itself to form Another element of the group
  3. Each element of the group obey associative law of combination
  4. Two elements of a group combine to form a third element of a group

Each group element has no reciprocal

Which is photochemical reaction?

  1. Photosynthesis
  2. Photography
  3. Vision reaction
  4. All of A, B, and C

All of A, B, and C

Which is not component of laser?

  1. Photo detector
  2. Laser medium
  3. Optical resonator
  4. Energy source

Photo detector

Which is a radioactive relaxation process?

  1. Internal conversion
  2. Phosphorescence
  3. Vibrational relaxation
  4. Intersystem crossing

Phosphorescence

Which acts as photosensitizer?

  1. Ni
  2. Cr
  3. Hemoglobin
  4. Chlorophyll

Chlorophyll

Methane belongs to ______.

  1. D∞h
  2. Tetrahedral group
  3. C∞v
  4. Octahedral group

Tetrahedral group

More Physical Chemistry MCQs

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  3. NUCLEAR CHEMISTRY MCQs
  4. CHEMICAL THERMODYNAMICS MCQs
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  6. CHEMICAL KINETICS MCQs
  7. SURFACE CHEMISTRY MCQs
  8. COLLOIDAL STATE MCQs
  9. ELECTROCHEMISTRY MCQs
  10. SPECTROSCOPY MCQs
  11. SOLUTION CHEMISTRY AND PHASE EQUILIBRIA MCQs
  12. PHOTOCHEMISTRY AND MOLECULAR SYMMETRY MCQs
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