Chapter 11 -

PARAMOUNT SCHOOL SYSTEM

Subject: Chemistry – I

Unit 11: Environmental Chemistry – Air

CONCEPT ASSESSMENT EXERCISE 11.1

What two gases make up most of the air?

The two gases that make up most of the air are:

Nitrogen (N₂): 78%

Oxygen (O₂): 21%

CONCEPT ASSESSMENT EXERCISE 11.2

1. What are pollutants?

Pollutants are anything that is in the air, water, or soil which has a harmful effect on some part of the environment. Pollutants damage the environment, health and quality of life.

2. List some effects of sulphur dioxide on human beings.

Effects of sulphur dioxide on human beings:

It is a powerful irritant readily absorbed in the respiratory system.
It aggravates the symptoms of people who suffer from asthma, bronchitis, emphysema, and other lung diseases.

3. List some of the air pollutants.

Some air pollutants are:

Industrial wastes
Herbicides
Pesticides
Insecticides
Particles of dust and smoke
Carbon monoxide
Nitrogen dioxide
Sulphur dioxide
Ozone
Lead-containing paints

CONCEPT ASSESSMENT EXERCISE 11.3

1. Write the names of main pollutants in the air.

Main Pollutants in the Air:

Carbon monoxide (CO)
Sulphur oxides (SO₂)
Nitrogen oxides (NO, NO₂)
Methane (CH₄)
Ground-level ozone (O₃)
Particulates

2. Complete the following reactions.

a) SO₂ _(g) + O₂ _(g) → SO₃ _(g)

b) C _(s) + O₂ _(g) → CO₂ _(g)

c) CO _(g) + O₂ _(g) → CO₂ _(g)

CONCEPT ASSESSMENT EXERCISE 11.4

1. Write three human activities that are responsible for air pollution.

Human activities that are responsible for air pollution:

Burning fossil fuels such as coal, petroleum, and natural gas.
Emissions from cars and other motor vehicles.
Factories and power plants that burn coal or oil.

2. Write three natural processes that are contributing in air pollution.

Natural processes that are contributing to air pollution:

Forest fires releasing smoke and dust particles.
Volcanic eruptions emitting clouds of dust and poisonous gases.
Termites and cows releasing large amounts of methane.

3. List main sources of the following air pollutants.

(a) SO₂:

The burning of fossil fuels in power plants, vehicles, industrial units, power generators and residential heating systems

(b) CO:

Incomplete burning of wood, fuels, and vehicle exhaust.

(c) NO₂:

Exhaust fumes of motor vehicles, power stations, and industries using fossil fuels.

CONCEPT ASSESSMENT EXERCISE 11.4

1. Define global warming

The warming of the atmosphere due to our influence on the greenhouse effect is called global warming. Global warming is caused by disturbing the natural balance of greenhouse gas concentrations in the atmosphere.

2. List some effects of global warming.

Effects of global warming:

Temperature of the earth will gradually increase.
The earth’s climate may change, affecting both the rate of rainfall and how much it rains.
Increased risks of flooding in some regions and drought in others.
Polar ice may melt, causing a significant increase in sea levels.
The atmosphere becomes hotter.

3. List some substances that are responsible for global warming.

Substances responsible for global warming:

Carbon dioxide (CO₂)
Methane (CH₄)
Water vapour

4. Establish the link between greenhouse effect and global warming.

The greenhouse effect naturally traps heat in the atmosphere, keeping Earth warm enough for life. Human activities, like burning fossil fuels and deforestation, increase greenhouse gases. This enhances the greenhouse effect, trapping more heat and causing the Earth’s temperature to rise, which leads to global warming.

CONCEPT ASSESSMENT EXERCISE 11.4

1. Define acid rain.

Acid rain is defined as rain having pH less than 5.6. Acid rain can often fall hundreds of kilometres from its source. Acid rain corrodes metals, stone structures and statues

2. Write names of gases that cause acid rain.

Gases that cause acid rain:

Sulphur dioxide (SO₂)
Nitrogen oxides (NO, NO₂)

3. What is the effect of acid rain on iron and marble? Give balanced chemical equation.

Iron:

Acid rain corrodes iron.

Fe_(s) + H₂SO_4(aq) → FeSO_4(aq) + H_2(g)

Marble:

Marble buildings and statues are disintegrated by acid rain.

CaCO_3(s)+ H₂SO_4(aq)→ CaSO_4(aq)+ H₂O_(g) + CO_2(g)

4. List some effects caused by acid rain.

Effects caused by acid rain:

Corrodes metals, stone structures, and statues
Kills fish and destroys trees
Makes lakes and rivers too acidic for living things to survive

5. Justify that acid rain is dangerous than normal rain

Acid rain has a much lower pH than normal rain, making it more corrosive and harmful to the environment, structures, and living organisms.

REVIEW QUESTIONS

Which gas has the highest percentage in the air?

(a) O₂ (b) CO₂ (c) N₂ (d) O₃

Which is/are responsible for acid rain?

(a) SO₂ (b) O₂ (c) Both NO₂ and SO₂ (d) CO₂

Which is reddish brown gas?
(a) NO (b) NO₂ (c) SO₂ (d) O₂
Most air pollution is caused by
(a) Ozone (b) Acid rain (c) Carbon monoxide (d) The burning of fossil fuels

2. Give short answer

i. List two main sources of acid rain.

The two main sources of acid rain are:

Sulphur dioxide (SO₂) from fossil fuels used in power plants.
Nitrogen oxides (NO and NO₂) from car exhausts.

ii. List four human activities which contribute to air pollution.

Four human activities that contribute to air pollution are:

Burning fossil fuels such as coal, petroleum, and natural gas.
Motor vehicles (cars and other motor vehicles).
Factories burning coal or oil.
Power plants that burn coal or oil.

iii. What is the importance of catalytic converter?

Catalytic converters are important because they help reduce air pollution. They change harmful gases from car exhausts, like carbon monoxide and nitrogen oxides, into less harmful substances like carbon dioxide and water. This helps keep the air cleaner.

iv. What is the role of automobile in air pollution?

Automobiles play a significant role in air pollution. Nearly half of air pollution comes from cars and other motor vehicles. They release harmful gases, such as carbon monoxide, nitrogen oxides, and sulfur oxides, into the air by burning fossil fuels like petroleum and natural gas.

v. Define global warming.

Substances responsible for global warming:

Carbon dioxide (CO₂)
Methane (CH₄)
Water vapour

3. Describe sources of air pollutants.

Sources of Air Pollutants:

Natural Sources:

Forest Fires: Release smoke and dust particles into the air.
Dust Storms: Contribute dust particles to the atmosphere.
Volcanoes: Emit clouds of dust, poisonous gases, and ash.
Termites and Cows: Release large amounts of methane.
Electrical Discharges: Produce nitrogen oxides in the atmosphere.

Human Activities:

Burning Fossil Fuels: Coal, petroleum, and natural gas used in power plants, vehicles, and industrial processes release various pollutants.
Motor Vehicles: Emit significant amounts of nitrogen oxides and carbon monoxide.
Factories and Power Plants: Release sulphur oxides, nitrogen oxides, and carbon monoxide from burning coal or oil.
Incomplete Combustion: Produces carbon monoxide and particulate matter from burning wood, fuels, and fossil fuels.
Incineration: Releases pollutants into the air.

4. Describe acid rain and its effects.

Acid Rain:

Acid rain is defined as rain having pH less than 5.6. Acid rain can often fall hundreds of kilometres from its source. Acid rain corrodes metals, stone structures and statues

Gases that cause acid rain:

Sulphur dioxide (SO₂)
Nitrogen oxides (NO, NO₂)

Effect of acid rain:

Acid rain may often fall hundreds of kilometers away from their sources. Acid rain corrodes metals, stone buildings and statues. Marble statues are slowly eroded by acid rain.

Sulphuric acid eats away metals to form water soluble salts and hydrogen.

Fe + H₂S0₄ FeSO₄ + H₂

Marble buildings and statues:

Marble buildings and statues are disintegrated by acid rain.

CaC0₃ + H₂SO₄ CaS0₄ + H₂O + CO₂

CaCO₃ + 2HNO₃ Ca(NO₃)₂ + H₂O + C0₂

Acid rain also kills fish, and destroys trees. Lakes and river may become too acidic for living things to survive. Trees destroyed by acid rain. Fish are killed by acid rain.

5. Describe global warming.

Global warming:

The warming of the atmosphere which is due to our influence on the greenhouse effect is known as global warming.

Substances responsible for global warming:

Carbon dioxide (CO₂)
Methane (CH₄)
Water vapour

Effect of Global warming:

Temperature of the earth will gradually increase.
The earth’s climate may change, affecting both the rate of rainfall and how much it rains.
Increased risks of flooding in some regions and drought in others.
Polar ice may melt, causing a significant increase in sea levels.
The atmosphere becomes hotter.

6. What is ground level ozone. Explain.

Ground-level ozone, often called smog, is a secondary pollutant produced by complex reactions between nitrogen oxides and volatile organic compounds (VOC) under sunlight. These reactions, called photochemical reactions, mainly occur in industrial and urban areas with emissions from industrial units and car engines. Ground-level ozone can irritate respiratory organs, cause asthma, and damage vegetation, reducing crop yields and harming forests.

7. Why is global warming often referred to as the greenhouse effect?

Global warming is called the greenhouse effect because greenhouse gases like water vapor, methane, and carbon dioxide trap heat in the atmosphere. These gases absorb and re-radiate infrared radiation from the Earth’s surface, keeping the planet warm. Increased greenhouse gases from human activities enhance this effect, raising temperatures and causing global warming.

8. Sulphur dioxide is a common pollutant from burning coal. State two effects caused by this pollutant.

Two effects caused by sulphur dioxide are:

It aggravates respiratory conditions such as asthma, bronchitis, emphysema, and other lung diseases.
It is responsible for acid rain and haze.

THINK TANK

1. Dibenzothiophene (C₁₂H₈S) is a common sulphur containing compound of coal. It is responsible for acid rain. How?

Dibenzothiophene (C₁₂H₈S) is a sulphur containing compound of coal on burning it produces sulphur dioxide. In the air sulphur dioxide is converted into sulphur trioxide, which is responsible for acid rain.

2. There have been various attempts to remove sulphur from coal before it is burned. Suggest reason.

Sulphur containing compounds in coal, when burned, produce sulfur dioxide (SO₂). In the air, sulfur dioxide is converted into sulfur trioxide (SO₃), which is responsible for acid rain. Therefore, efforts have been made to remove sulfur from coal before burning it.

3. Examine the option there are some ways to reduce pollution caused by cars?

Ways to reduce pollution caused by cars:

Install Catalytic Converters: Use catalysts in car exhaust systems to convert harmful gases into less harmful substances.
Promote Electric Vehicles: Encourage the use of electric cars to reduce fossil fuel consumption.
Enhance Public Transport: Improve and promote public transportation to decrease individual car use.
Encourage Walking and Cycling: Support walking and cycling to reduce reliance on cars.
Implement Strict Regulations: Enforce laws requiring the installation of catalytic converters and other pollution-reducing technologies in cars.

4. Certain human activities are responsible for a significant increase in greenhouse effect, argue.

Human activities increase the amount of greenhouse gases. These gasses play important role in global warming. Following human activities are responsible for greenhouse effect:

Cutting forests (deforestation).
Burning of fossil fuels such as coal, oil and gas.
Household, industrial and livestock waste.
Use of leaded paints.

18. As a global citizen, how can you play a part to reduce air pollution at a personal level? Argue.

As a global citizen, we take following steps to reduce air pollution at a personal level.

Walk short distances or ride cycles instead of using vehicles.
Use Catalytic Converters in vehicles.
By growing more plants.
Dispose house hold waste at proper places.
Use public transport.