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Atmospheric pollutants

Carbon and soot are not the only atmospheric produced by the of . Sulfur dioxide and of nitrogen may be produced too.

Sulfur dioxide

Many hydrocarbon fuels naturally contain sulfur . When the fuels are burned, the sulfur to form sulfur dioxide gas:

Sulfur + oxygen 鈫 sulfur dioxide

S(s) + O2(g) 鈫 SO2(g)

Sulfur dioxide in water in the clouds to form sulfurous acid:

SO2(g) + H2O(l) 鈫 H2SO3(aq)

Oxygen in the air reacts with sulfurous acid to form sulfuric acid:

H2SO3(aq) + 陆O2(g) 鈫 H2SO4(aq)

The of the two falls from the clouds as .

Question

Explain why sulfurous acid is oxidised when it forms sulfuric acid.

Effects of acid rain

Acid rain damages the natural and built . For example, it:

  • reacts with and rocks such as , weakening and damaging buildings and statues
  • damages plants and trees, making them lose their leaves and die
  • makes rivers and lakes too for some aquatic life to survive
Stone carvings damaged by acid rain
Image caption,
These stone carvings have been damaged by acid rain

Oxides of nitrogen

High temperatures are reached when fuels are burned in engines. At these high temperatures, nitrogen and oxygen from the air can react together to produce oxides of nitrogen. For example:

Nitrogen + oxygen 鈫 nitrogen monoxide

N2(g) + O2(g) 鈫 2NO(g)

Nitrogen monoxide gas can be oxidised further in air to produce nitrogen dioxide gas, NO2.

Nitrogen dioxide

These two oxides of nitrogen are together represented by the formula NOx. They are atmospheric pollutants. They can react in sunlight with other substances to produce a hazy, harmful . Nitrogen dioxide is . It can cause and other lung diseases. It also dissolves in water in the clouds, forming an acidic solution that contributes to acid rain.

Question

Write a balanced equation for the reaction between nitrogen monoxide and oxygen, forming nitrogen dioxide. Include state symbols in your answer.