---
title: "Carbon dioxide and atmospheric pollution"
subject: "Engineering Chemistry"
chapter: 3
key: "semester_2/engineering_chemistry:co2-pollution"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/co2-pollution
site: BCT Engineering
---

# Carbon dioxide and atmospheric pollution

Engineering Chemistry · Chapter 3: Environmental Chemistry

- Asked in: 2073 Magh, 2 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/co2-pollution
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-3

## Question

How does carbon dioxide cause atmospheric pollution?

## Short answer

CO₂ traps infrared radiation as a greenhouse gas, causing global warming, ice melt, and sea-level rise. It also dissolves in oceans forming carbonic acid, lowering pH and threatening corals and shellfish. Elevated CO₂ concentration is primarily from burning fossil fuels.

## Answer

Carbon dioxide is not toxic, but its excess in the atmosphere is a pollutant because:

- **Greenhouse effect:** CO₂ absorbs infrared radiation emitted by the earth and traps heat, leading to global warming. About 60 % of the enhanced greenhouse effect is due to CO₂.
- **Rising concentration:** burning of coal, oil and wood, cement production and deforestation have raised it from about 280 ppm (before industrialisation) to over 420 ppm today.
- **Consequences:** melting of ice, sea-level rise and climate change.
- **Ocean acidification:** dissolved CO₂ forms carbonic acid (CO₂ + H₂O ⇌ H₂CO₃), lowering ocean pH and harming corals and shellfish.
- In very high concentration in closed spaces it displaces oxygen and causes suffocation.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why is excess CO2 a pollutant though not toxic?
   A. It is a strong poison in air
   B. It destroys ozone
   C. It absorbs infrared and traps heat, causing global warming
   D. It forms acid rain with SO2
   Answer: C. CO2 contributes about 60% of the enhanced greenhouse effect. (Key point: Greenhouse)

2. What is ocean acidification?
   A. Dissolved CO2 forms H2CO3, lowering ocean pH and harming corals and shellfish
   B. CO2 raises ocean pH
   C. CO2 forms H2SO4 in the sea
   D. CO2 warms water only
   Answer: A. CO2 + H2O <-> H2CO3. (Key point: Ocean acidification)

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