5.5Chapter 5: Acids and Alkalis

Acid rain — Alhussan Chemistry - Stage 7 Revision Notes & Topical Questions

5 min read 8 parts Lesson 5 of 7 4 quizzes

📚 Alhussan Chemistry - Stage 7 Hub / Topical Revision

0%read

Lesson summary

5.5 Acid rain — Environmental Causes, Effects and Soil Liming — Alhussan International Academy — Chemistry (Stages 7–9) notes: Explain how acid rain forms, its effects on buildings, trees and lakes, and how its impact can be reduced.Normal rain — it is slightly acidic (about pH 5…

Cars and lorries
Burning rubbish
Power stations
Sulfur dioxide
Nitrogen oxides
Buildings and statues

Section 1 of 8What acid rain is

Normal rain

Normal rain it is slightly acidic (about pH 5.6) because carbon dioxide dissolves in it to form carbonic acid.

Acid rain

Acid rain rain with a pH below about 5.0, caused mainly by sulfur dioxide and nitrogen oxides dissolving in water droplets in clouds.

They form sulfuric and nitric acids.

Spread

Spread winds carry the pollution hundreds of kilometres, so acid rain can fall in different countries from where it was produced.

Section 2 of 8Sources of acidic gases

Cars and lorries

Cars and lorries they burn fossil fuels and make acidic gases.

Factories

Factories some make glass, process leather or make products from oil and produce acidic waste gases.

Burning rubbish

Burning rubbish it makes acidic gases.

Power stations

Power stations those that burn coal make waste products including acidic gases, and some neutralise the gases while others send them into the air.

Sulfur dioxide

Sulfur dioxide it forms when fossil fuels containing sulfur are burned and when sulfur-containing metal ores are roasted, and volcanoes release it.
sulfur + oxygen → sulfur dioxide; sulfur dioxide + water + oxygen → sulfuric acid.

Nitrogen oxides

Nitrogen oxides they form when nitrogen and oxygen in the air react at the high temperatures in car engines and furnaces, and during lightning.

Section 3 of 8Effects of acid rain

Effects of acid rain

Buildings and statues

Buildings and statues limestone and marble, which are calcium carbonate, are eroded.
Nitric acid + calcium carbonate → calcium nitrate + water + carbon dioxide.
Sulfuric acid + calcium carbonate → calcium sulfate + water + carbon dioxide.
The marble is damaged for ever.

Lakes and rivers

Lakes and rivers they become acidic, so some plants and animals cannot live in them.
Aluminium is released from soil into water and is toxic.

Trees

Trees acid rain damages leaves and washes nutrients such as magnesium and calcium out of the soil.

Rock

Rock acid rain damages some types of rock, and scientists think it may have caused a landslide in China.

Metal structures

Metal structures they corrode faster.

Section 4 of 8Case study: the Taj Mahal

Problem

Problem the white marble of the Taj Mahal in India is turning yellow because acid rain reacts with it.
Cars, lorries, factories and burning rubbish near it make the acidic gases.

Possible actions

Possible actions factories can neutralise their acidic waste, and people can drive electric or hydrogen cars, walk or cycle.
Some methods are easier, more effective or cheaper than others.

Decision

Decision the government used science to evaluate methods and also considered the jobs factories provide.
It told factories to neutralise waste or move away and banned petrol and diesel vehicles in the area.
Some people obeyed and others did not, and in 2021 acid rain continued to damage the Taj Mahal.

Lesson

Lesson every possible action has advantages and disadvantages, and governments need to evaluate them before deciding.

Section 5 of 8Reducing the problem

Prevention

Prevention it is better than cure.
Remove sulfur from fuel before burning.
Use flue gas desulfurisation in power stations, where calcium carbonate or calcium oxide reacts with sulfur dioxide.
Fit catalytic converters to cars to change nitrogen oxides into nitrogen.
Use cleaner methods to make electricity, such as wind turbines or solar cells, and use public transport.

International limits

International limits governments agree limits on emissions.

Repairing damage

Repairing damage liming adds calcium hydroxide (slaked lime) or calcium carbonate to acidic lakes and soils to neutralise the acid and raise the pH.
It is a short-term fix and costly, so reducing emissions is the long-term solution.

Section 6 of 8Data and decisions

Monitoring

Monitoring scientists collect rainwater and measure its pH at different places and times.

pH change

pH change if the average pH falls from 5.6 to 4.2, the rain has become about 25 times more acidic.

Regulation

Regulation after laws lowered emissions in Europe and North America the pH of rain in many areas rose.
Recovery is slow because soils and lake sediments hold acid for years.

Cost

Cost desulfurisation raises electricity prices but reduces damage to health, buildings and farming.

Natural sources

Natural sources volcanoes also contribute to acid rain.

Section 7 of 8Key terms

Term	Meaning
Acid rain	Rain with a pH below about 5.0 caused by sulfur dioxide and nitrogen oxides.
Sulfur dioxide	An acidic gas made when sulfur-containing fuels burn.
Nitrogen oxides	Acidic gases made at high temperatures in engines.
Liming	Adding calcium hydroxide or carbonate to neutralise acidic soil or water.
Flue gas desulfurisation	Removing sulfur dioxide from power station gases.
Catalytic converter	A device that changes harmful exhaust gases into less harmful ones.