Engineering Chemistry Multiple Choice Questions on “Photochemical Reactions”.
1. The reactions which are caused by heat and in absence of light is called _____
a) Photochemical reactions
b) Dark reactions
c) Reversible reaction
d) Reversible photochemical reaction
Answer: b
Clarification: The reactions which are caused by heat and in absence of light are called thermal or dark reactions. A reaction that takes place by absorption of light radiations of a specific wavelength is called photochemical reaction.
2. In photochemical reactions, absorption of _____ radiations takes place.
a) ultraviolet and visible
b) radio
c) only visible
d) visible and x-rays
Answer: a
Clarification: Absorption of visible and ultraviolet radiations can only take place in a photochemical reaction. Wavelength of absprbed radiations ranges from 2000 – 8000 Å.
3. In photochemical reactions, the presence of light is not required for the reaction to take place.
a) true
b) false
Answer: b
Clarification: In photochemical reactions, presence of light is the primary requirement for the reaction to take place. It involves absorption of light radiations.
4. Ozone is formed by ______ dissociation of molecular oxygen into individual oxygen atoms.
a) photochemical
b) thermochemical
c) thermal
d) ionic
Answer: a
Clarification: Molecular oxygen undergoes photochemical dissociation into individual oxygen atoms. These oxygen atoms are reacted with molecular oxygen to form ozone.
5. Which of the following is an example of photochemical reaction?
a) Photosynthesis
b) Decomposition of ammonia
c) Formation of NaOH
d) Decomposition of HCl
Answer: a
Clarification: Photosynthesis is an example of photochemical reaction. In photosynthesis, light energy is captured by the chlorophyll present in the thylakoids of the chloroplast for the production of photons. Water is splitted by photons from light energy and it enables ATP production that drives the entire process.
6. Which of the following are the principle laws of photochemistry?
a) Grothus-Draper and Stark-Einstein law
b) Raoult’s and Dalton’s law
c) Raoult’s and Henry’s law
d) Lambert’s and Beer’s law
Answer: a
Clarification: Two fundamental principles of photochemistry are there. They are Grothus-Draper law and Stark-Einstein law.
7. Mercaptans can be produced by photochemical addition of ______ to alpha olefins.
a) hydrogen sulphide
b) sulphur
c) hydrogen
d) paraffins
Answer: a
Clarification: Mercaptans can be produced by photochemical addition of hydrogen sulfide to alpha olefins. In this method, there is a provision for increasing the total conversion of reactants to mercaptans by including carbon disulfide in the reaction mixture.
8. Vision is initiated by a photochemical reaction of ______
a) Rhodopsin
b) Hydrogen Chloride
c) Mercapton
d) Enzymes
Answer: a
Clarification: Vision is initiated by a photochemical reaction of rhodopsin. It is the primary photoreceptor molecule of vision.
9. Medicine bottles are often made with darkened glass _______
a) to prevent the drug from photodegradation
b) to allow the photodegradation of drug
c) to reduce the cost
d) to allow oxidation of drug
Answer: a
Clarification: Medicine bottles are often made with darkened glass to prevent the drugs from photodegradation. Generally, brown color is used because of its ability to prevent UV light from degrading the potentially photosensitive contents through photochemical reactions.
10. In _____ reactions, molecules absorbing light do not themselves react but induce other molecules to react.
a) Photosensitized
b) Thermal
c) Irreversible
d) Dark
Answer: a
Clarification: The reactions in which molecules absorbing light do not themselves react but induce other molecules to react are called photosensitized reactions. The reactions which are caused by heat and in absence of light is called thermal or dark reactions.