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

Ozone layer depletion is mainly caused by:
A. Carbon monoxide
B. Ammonia
C. Sulphur dioxide
D. Chlorofluorocarbons (CFCs)
Answer: Option D
Solution (By JKExamLibrary)
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.

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Practice More chemistry Questions

Question #1
Crystallization is used to purify:
A. Solids
B. Liquids
C. Plasma
D. Gases

Correct Answer: Option A


Explanation:
Crystallization separates a pure solid from a solution by cooling or evaporating the solvent. Impurities remain in the mother liquor. Example: purifying copper sulfate. Distillation for liquids; filtration for insoluble solids.

This question belongs to: Science chemistry
Question #2
CNG is considered a cleaner fuel than petrol because it produces:
A. Sulfur dioxide
B. More oxides of nitrogen
C. Less CO₂ and negligible particulate matter
D. More CO₂

Correct Answer: Option C


Explanation:
CNG (methane) has a higher H/C ratio, so combustion produces less CO₂ per unit energy compared to petrol/diesel. It also burns completely without generating smoke or particulate matter, and contains no sulfur, thus no SO₂. It reduces NOx and unburned hydrocarbons. It is used in vehicles and is safer in spills because it is lighter than air and disperses quickly.

This question belongs to: Science chemistry
Question #3
Sodium chloride (table salt) is obtained from seawater by:
A. Filtration
B. Distillation
C. Sublimation
D. Evaporation

Correct Answer: Option D


Explanation:
Salt is obtained by evaporation of seawater in shallow ponds. Water evaporates leaving salt behind. Filtration cannot separate dissolved salt. Distillation would give pure water, not salt. Sublimation for sublimable solids.

This question belongs to: Science chemistry