Pick the incorrect statement (ozone thickness, 2-stroke vs 4-stroke emissions, mercury toxicity) From the following, identify the statement that is wrong based on established environmental and engine-emission facts.
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ALow ozone layer thickness in polar regions is due to cold climatic conditions
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BAmount of unburnt hydrocarbons emitted by two stroke petrol engine is more as compared to that emitted by a four stroke engine.
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CCarbon monoxide present in the two stroke petrol engine exhaust is much less as compared to that emitted from a four stroke engine.
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DMercury as a pollutant can enter the blood stream & the digestive system/ lungs and is responsible for causing minamate disease.
Answer
Correct Answer: Carbon monoxide present in the two stroke petrol engine exhaust is much less as compared to that emitted from a four stroke engine.
Explanation
Introduction / Context:This item mixes atmospheric science and engine-emissions knowledge. The goal is to spot the incorrect claim among statements about polar ozone depletion, two-stroke engine emissions, and mercury health effects. Accurate classification is essential for air quality management and public health.
Given Data / Assumptions:
- Two-stroke spark-ignition engines typically run with fuel-oil mix and exhibit scavenging losses.
- Four-stroke engines generally burn fuel more completely, with less short-circuiting.
- Polar ozone loss is associated with cold stratospheric conditions enabling heterogeneous chlorine chemistry.
- Minamata disease is mercury poisoning with severe neurological effects.
Concept / Approach:Two-stroke petrol engines usually emit higher unburned hydrocarbons and often higher CO due to short-circuiting of fresh charge and richer mixtures. Therefore, the assertion that their CO is “much less” than four-stroke engines is wrong. The other statements are broadly consistent with fundamentals: polar ozone thinning is linked to extremely cold stratospheric temperatures that form polar stratospheric clouds, and mercury indeed causes Minamata disease.
Step-by-Step Solution:
Evaluate (b): two-strokes → higher unburnt HC than four-strokes → statement is correct.Evaluate (c): claims two-strokes have much less CO → contradicted by typical emission profiles → incorrect.Evaluate (a): cold stratosphere enables chemistry that depletes ozone → broadly true contextually.Evaluate (d): mercury toxicity causes Minamata disease → correct.Verification / Alternative check:Emission inventories and dynamometer tests show two-strokes often exceed four-strokes in CO and HC emissions when uncontrolled, validating the choice.
Why Other Options Are Wrong:
(a) Although simplified, the cold stratosphere is indeed a key enabler of polar ozone loss.(b) Correct: two-stroke engines typically emit more unburnt hydrocarbons.(d) Correct: mercury exposure leads to Minamata disease.Common Pitfalls:Over-interpreting (a) as the sole cause; chemistry involving chlorine/bromine is the mechanistic driver, with cold conditions enabling it.
Final Answer:Carbon monoxide present in the two stroke petrol engine exhaust is much less as compared to that emitted from a four stroke engine.