Photochemistry Quiz | Photochemistry Multiple Choice Questions and Answers
Questions
1
The fact that the fluorescence wavelength is often much longer than the irradiation wavelength (Stokes shift) is a consequence of which phenomenon?
Answer: the Franck–Condon principle
2
The quantum efficiency of a photochemical reaction is defined as _______
Answer: ratio of molecules decomposed in a given time to the number of quanta absorbed in the same time
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3
Which of the following are the reactions in which molecules absorbing light do not themselves react but induce other molecules to react?
Answer: Photosensitized reactions
4
The reactions which are caused by heat and in absence of light is called _____
Answer: Dark reactions
5
Ozone is formed by ______ dissociation of molecular oxygen into individual oxygen atoms.
Answer: photochemical
6
Which of the following is an example of photochemical reaction?
Answer: Photosynthesis
7
Which of the following are the principle laws of photochemistry?
Answer: Grothus-Draper and Stark-Einstein law
8
Mercaptans can be produced by photochemical addition of ______ to alpha olefins.
Answer: Hydrogen Sulphide
10
Medicine bottles are often made with darkened glass _______
Answer: to prevent the drug from photodegradation
11
In _____ reactions, molecules absorbing light do not themselves react but induce other molecules to react.
Answer: Photosensitized
12
In photochemical reactions, absorption of _____ radiations takes place.
Answer: ultraviolet and visible
13
A substance absorbs 2.0 x 1016 quanta or radiations per second and 0.002 mole of it reacts in 1200 seconds. What is the quantum yield or the reaction (N = 6.02 x 1023)?
Answer: 50
14
Which of the following will result in deviation from Beer’s law?
(A) Change in a refractive index of medium
(B) Dissociation of analyte on dilution
(C) Polychromatic light
(D) Path length of cuvette
Answer: A, B and C
15
A 0.1 M solution of compound A shows 50% transmittance when a cell of 1 cm width is used at λ1 nm. Another 0.1 M solution of compound B gives the optical density value of 0.1761 using 1cm cell at λ1 nm. What will be the transmittance of a solution that is simultaneously 0.1 M in A and 0.1 M in B using the same cell and at the same wave length? [log 1.301; log 1.4771; log 50 = 1.699].
Answer: 33.3%
16
What are the appropriate reasons for the deviation from the Beer’s law among the following?
(A) Monochromaticity of light
(B) Very high concentration of analyte
(C) Association of analyte
(D) Dissociation of analyte
Answer: B, C and D
17
The molar extinction coefficient of B (MW = 180) is 4 x 103 L mol-1 cm-1. One-liter solution of C which contains 0.1358 g pharmaceutical preparation of B, shows an absorbance of 0.411 in a 1 cm quartz cell. What is the percentage (w/w) of B in the pharmaceutical preparation?
Answer: 13.60
18
Which of the following instruments is used to measure the energy of the monochromatic radiation most accurately?
Answer: Thermopile
19
Which regions of the light radiations of the visible ultraviolet lying between – wavelength are chiefly concerned in bringing about photochemical reactions?
Answer: 8000 Å and 2000 Å
20
Which of the following is an incorrect statement?
Answer: Photochemical reactions are caused by absorption of ultraviolet only
