Oxides of nitrogen and pollution
| English | Chinese | Pinyin |
|---|---|---|
| oxides of nitrogen | 氮氧化物 | dàn yǎng huà wù |
| acid rain | 酸雨 | suān yǔ |
| catalytic converter | 催化转化器 | cuī huà zhuǎn huà qì |
| photochemical smog | 光化学烟雾 | guāng huà xué yān wù |
| nitric acid | 硝酸 | xiāo suān |
Pollution from the engine
- Oxides of nitrogen 氮氧化物 ($\text{NO}$ and $\text{NO}_2$, together NOₓ) pollute the air.
- They come from lightning and from engines.
- They cause smog and acid rain 酸雨 — but we can remove some.
NOx pollution route
Trace nitrogen oxides from hot engines to environmental harm.
Oxides of nitrogen from car engines contribute to acid rain and photochemical smog.
NOₓ are atmospheric pollutants.
Where NOₓ comes from
- natural: lightning gives enough energy for $\text{N}_2$ and $\text{O}_2$ in the air to combine.
- man-made: the high temperature in a car engine makes them react: $\text{N}_2 + \text{O}_2 \rightarrow 2\text{NO}$.
Oxides of nitrogen contribute to smog and air pollution
Oxides of nitrogen (NOₓ) are produced by:
Lightning (natural) and the heat of internal combustion engines both make N₂ and O₂ combine into NO.
Match each NOₓ fact.
Each item links the term to its correct meaning.
Catalytic converters 催化转化器
- A catalytic converter cleans the exhaust by letting harmful gases react to harmless ones:
$$2\text{NO} + 2\text{CO} \rightarrow \text{N}_2 + 2\text{CO}_2$$
A catalytic converter turns harmful NO and CO into harmless N2 and CO2
In a catalytic converter, NO and CO react to form:
2NO + 2CO → N₂ + 2CO₂; the harmful gases become harmless ones.
Smog and acid rain
- In sunlight, NOₓ reacts with unburned hydrocarbons to form PAN, part of brown photochemical smog 光化学烟雾.
- NOₓ makes acid rain two ways: $\text{NO}_2$ forms nitric acid 硝酸 directly, and it also catalyses the oxidation of $\text{SO}_2$ to $\text{SO}_3$ (→ sulfuric acid).
Nitrogen and sulfur oxides form nitric and sulfuric acid in rain
How does NO₂ contribute to acid rain?
NO₂ dissolves to form nitric acid, and it also speeds up SO₂ → SO₃, which forms sulfuric acid.
Photochemical smog forms when NOₓ reacts in sunlight with unburned hydrocarbons to make:
In sunlight NOₓ and hydrocarbons form PAN, a harmful part of the brown photochemical smog.
You've got it
- NOₓ comes from lightning (natural) and the high temperature in engines ($\text{N}_2 + \text{O}_2 \rightarrow 2\text{NO}$)
- a catalytic converter: $2\text{NO} + 2\text{CO} \rightarrow \text{N}_2 + 2\text{CO}_2$
- NOₓ → photochemical smog (PAN) and acid rain (nitric acid + catalysing $\text{SO}_2 \rightarrow \text{SO}_3$)