PHOTOCHEMISTRY AND MOLECULAR SYMMETRY MCQs
One mole of photon is called _____ .
- Quantum
- Energy Packet
- Einstein
- None of A, B, and C
Einstein
The emission of light in a biological reaction is called ___.
- Fluorescence
- Phosphorescence
- Chemiluminescence
- 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
- Photochemical equivalence law
- Einstein law
- Grotthus-Draper law
Grotthus-Draper law
____ is the glow of yellow phosphorous as a result of slow oxidation in air.
- Photolysis
- Luminescence
- Bioluminescence
- Chemiluminescene
Chemiluminescene
The spin multiplicity of the electronic state is equal to
- S+1
- 2S + 2
- 2S – 2
- 2S + 1
2S + 1
Reactions in which molecules absorbing light do not themselves react but induce other molecules to react are called
- Chain reactions
- Free radical reactions
- Reversible reactions
- 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 _____ .
- Phosphorescence
- Scattering
- Fluorescence
- Chemiluminescence
Fluorescence
Which statement is not true with respect to photochemical reactions?
- Temperature has significant effect on rate of these reactions
- Free energy of these reactions may be positive or negative
- Light intensity affects these reactions
- 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?
- The primary photochemical process may be reversed
- The active molecules may collide with other molecules and activate these molecules
- The reaction may be exothermic and heat evolve may activate other molecules
- Formation of reactive intermediates which may act as catalyst
The primary photochemical process may be reversed
According to “The Lambert-Beer law” , ______
- Transmission is directly proportional to path length
- Transmission is directly proportional to concentration
- Absorbance is directly proportional to concentration & path length
- 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 _____ .
- Inter-system crossing
- Phosphorescence
- Internal conversion
- Fluorescence
Inter-system crossing
When a transition occurs between states the same multiplicity without emitting light, the process is called
- Fluorescence
- Quenching
- Intersystem crossing
- Internal conversion
Internal conversion
A molecule returns from the first excited triplet sate to the ground singlet state. The light emitted is called _____ .
- Inter-system crossing
- Phosphorescence
- Fluorescence
- Quenching
Phosphorescence
The quantum yield of a photochemical reaction is
- Can have any value 0 depending on the reaction
- Forever equal to unity
- Forever greater than unity
- Forever less than unity
Can have any value 0 depending on the reaction
Which reaction does not take place with light radiation?
- Double displacement
- Reduction
- Polymerization
- Oxidation
Double displacement
Which radiations are photo chemically active?
- Micro waves
- Radio waves
- Ultraviolet
- Infrared
Ultraviolet
The wavelength of fluorescent light () is related to the wavelength of absorbed light (b) by
- λf > λab
- λf > λab
- λf λab
- λf < λab
λf > λab
The value of an Einstein
- Is independent of wavelength
- Depends on the temperature of the absorbing system
- Increases with increase in wavelength
- Decreases with increase in wavelength
Decreases with increase in wavelength
Ethylene belongs to
- C2v group
- D∞h group
- C2v group
- D2v group
D2v group
Which molecules have center of symmetry?
- H2O
- HCI
- H2SO4
- CO2
CO2
According to the Grotthus-Draper law
- Only absorbed light is effective in producing photochemical changes
- Only light between certain wavelengths is effective in photochemical changes
- The light absorbed is proportional to its intensity
- 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?
- NH3
- H₂S
- BF3
- H₂O
NH3
The branch of chemistry dealing with the study of reactions in the UV-visible region of the spectrum is called _____ .
- Kinetics
- Cryoscopy
- Surface chemistry
- Photochemistry
Photochemistry
A line, a point or a plane about which a symmetry operation is performed, is called _____ .
- Symmetry
- Symmetry operation
- Reflection
- Inversion element
Symmetry
Which items is not symmetry element?
- Optical activity
- Inversion center
- Improper rotation
- Plane of symmetry
Optical activity
What is the reverse of a photochemical reaction?
- Phosphorescence
- Photosensitization
- Fluorescence
- Chemiluminescence
Chemiluminescence
Which symmetry element leaves the molecule or an object unchanged?
- Identity
- Improper rotation
- Inversion axis
- Proper rotation
Identity
In proper rotation (Cn), an object is rotated through an angle of
- π /n radians
- 4π/n radians
- 3π/n radians
- 2π/n radians
2π/n radians
Which molecules possess horizontal mirror plane?
- PF3
- Water
- Ammonia
- H2S
PF3
What is the point group of CO2?
- D6h
- C4v
- C6v
- D2h
D6h
A photosensitizer is a substance that
- Initiates a photochemical reaction
- Decreases the speed of a chemical reaction
- Stops the photochemical reaction
- Increases the speed of a chemical reaction
Initiates a photochemical reaction
The extinction coefficient has the units
- cm³ mol-1
- cm² mol-1
- mol cm–²
- mol cm-3
cm² mol-1
Which techniques is helpful and used to study photochemical processes?
- Flash photolysis
- Dilatometry
- Viscometry
- Polarimetry
Flash photolysis
CO belongs to which group?
- C2v
- D2h
- D∞h
- C∞v
C∞v
How many planes of symmetry are present in benzene?
- 6 planes
- 3 planes
- 5 planes
- 1 plane
6 planes
PF5 belongs to which point group
- D2h
- D4h
- D5h
- D3h
D3h
The point group of XeOF4 is
- C6v
- D2h
- D4h
- C4v
C4v
What is the point group of BF3?
- D3h
- C4v
- C3v
- D2h
D3h
Linear molecules have ____ axis of rotation
- C∞
- C2
- C3
- C1
C∞
In C-axis of rotation, an object is rotated through an angle of
- 90°
- 180°
- 100°
- 120°
90°
What is the point group of benzene?
- D6h
- C4v
- C6v
- D2h
D6h
What is the point group of SF6?
- C6v
- C4v
- Tetrahedral
- Octahedral
Octahedral
Which is a non-radioactive relaxation process?
- Internal conversion
- Intersystem crossing
- Vibrational relaxation
- All of A, B, and C
All of A, B, and C
Which molecules have rotation-reflection axis?
- Methane
- Allenes
- Staggered ethene
- All of A, B, and C
All of A, B, and C
Which molecules belong to special point group D∞h?
- CO2
- H2
- Cl2
- All of A, B, and C
All of A, B, and C
In a photochemical reaction
- ΔF is positive
- ΔF is negative.
- ΔF is 0
- None of A, B, and C
ΔF is positive
Which statement is not true with respect to group theory?
- Each group element has no reciprocal
- An element combines with itself to form Another element of the group
- Each element of the group obey associative law of combination
- Two elements of a group combine to form a third element of a group
Each group element has no reciprocal
Which is photochemical reaction?
- Photosynthesis
- Photography
- Vision reaction
- All of A, B, and C
All of A, B, and C
Which is not component of laser?
- Photo detector
- Laser medium
- Optical resonator
- Energy source
Photo detector
Which is a radioactive relaxation process?
- Internal conversion
- Phosphorescence
- Vibrational relaxation
- Intersystem crossing
Phosphorescence
Which acts as photosensitizer?
- Ni
- Cr
- Hemoglobin
- Chlorophyll
Chlorophyll
Methane belongs to ______.
- D∞h
- Tetrahedral group
- C∞v
- Octahedral group
Tetrahedral group
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