What causes acid rain?

Appeared in: Bihar CHO -2019

Explanation

Acid rain is formed when primary air pollutants, sulfur dioxide (SO₂) and nitrogen oxides (NOx), react with water (H₂O) in the atmosphere.
This reaction creates secondary pollutants, namely sulfuric acid (H₂SO₄) and nitric acid (HNO₃), which then fall to the earth as acid precipitation.
The primary sources of these pollutants are the burning of fossil fuels for electricity generation, as well as emissions from vehicles and industrial processes.
Although the option uses 'SO₄' which is chemically imprecise (it should be SO₂ or SO₃), it is the only option that correctly pairs a sulfur compound with water (H₂O), the essential ingredient for the reaction.

Option A: This option is incorrect. While NO (nitric oxide) is a precursor to acid rain, the primary reaction that forms the acid involves water, not just the combination of a sulfate ion and nitric oxide.
Option B: This option is incorrect. N₂O (nitrous oxide) is a potent greenhouse gas but is not a primary precursor for acid rain. The main nitrogen oxides involved are NO and NO₂.
Option D: This option is incorrect. N₂ is atmospheric nitrogen, which is a relatively inert gas and does not directly participate in the formation of acid rain.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Chemical formation of acid rain as background academic context rather than a clinical decision trigger.
While acid rain itself is an environmental issue, the precursor pollutants (SO₂ and NOx) have direct health impacts.
Inhalation of fine sulfate and nitrate particles can penetrate deep into the lungs, causing or worsening respiratory conditions such as asthma, bronchitis, and other lung diseases.
Nurses in industrial or heavily polluted urban areas should be aware of the higher incidence of respiratory ailments and educate patients on minimizing exposure during high-pollution days.

How to Approach the Question

First, identify the core concept of the question, which is the cause of 'acid rain'.
Recall the basic chemical process of acid rain formation. It involves industrial pollutants reacting with a natural atmospheric component.
The key pollutants are sulfur oxides (SOx) and nitrogen oxides (NOx).
These pollutants react with water (H₂O) in the atmosphere to form strong acids (sulfuric acid and nitric acid).
Evaluate the given options to see which one best represents this reaction. The option including water (H₂O) is the most likely answer.
Eliminate the other options based on chemical principles. N₂ is inert, and reactions without water do not form the acids characteristic of acid rain.

Concept Tested & Keywords

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E6 Comprehensive Textbook of Community Health NursingShyamala D part 1 (pp 26-389 of 389) p. 136-138

E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) p. 51-53

Practise the full Bihar CHO -2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.