Ozone layer depletion is mainly caused by: MCQ with Answer and Explanation

Question
Ozone layer depletion is mainly caused by:
A. Carbon monoxide
B. Chlorofluorocarbons (CFCs)
C. Sulphur dioxide
D. Ammonia
Answer: Option B
Solution (By JKSSB Mock Tests)
CFCs release chlorine atoms under UV radiation in the stratosphere, which catalytically destroy ozone molecules. CO causes smog and is poisonous, SO₂ causes acid rain, ammonia is not a major ozone depleter. The Montreal Protocol phased out CFCs to protect the ozone layer.
This question belongs to: Science chemistry
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Practice More chemistry Questions

Question #1
During the electrolysis of acidified water, the volume ratio of hydrogen to oxygen collected is:
A. 1:1
B. 1:2
C. 2:1
D. 3:1
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Correct Answer: Option C

Explanation:
Water decomposes as 2H₂O → 2H₂ + O₂. So 2 volumes of H₂ for every 1 volume of O₂, ratio 2:1. Hydrogen collected at cathode, oxygen at anode.
This question belongs to: Science chemistry
Question #2
Sodium hydroxide (caustic soda) is manufactured by:
A. Ostwald process
B. Contact process
C. Chlor-alkali process
D. Haber process
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Correct Answer: Option C

Explanation:
The chlor-alkali process electrolyzes concentrated NaCl solution (brine) to produce NaOH, Cl₂, and H₂. 2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂. The mercury, diaphragm, or membrane cell can be used. Contact process is for H₂SO₄, Haber for NH₃, Ostwald for HNO₃.
This question belongs to: Science chemistry
Question #3
Dmitri Mendeleev's periodic table was based on:
A. Number of neutrons
B. Atomic mass and chemical properties
C. Mass number
D. Atomic number
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Correct Answer: Option B

Explanation:
Mendeleev arranged elements in order of increasing atomic mass, grouping those with similar properties. He left gaps for undiscovered elements. Modern table uses atomic number.
This question belongs to: Science chemistry
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