Chapter 19: Air and atmosphere

Question 1

What is the composition of dry air?

Answer 1

• 78% Nitrogen
• 21% Oxygen
  1% Other gases, which is mainly argon (0.97%)

Question 2

State the uses of nitrogen

Answer 2

• In liquid form used as a cooling agent
• to manufacture ammonia in the Haber Process, which in turn is used to make ammonium salts and nitrate salts

Question 3

State the uses of oxygen

Answer 3

1. It is used as an oxidising agent to support combustion
2. To support respiration
3. To remove carbon impurities

Question 4

Noble gases

Answer 4

1. To maintain an inert atmosphere e.g. argon in filament lamps
2. Helium can be used as a lifting agent in balloons and airships

Question 5

State the source of SO2

Answer 5

Combustion of sulfur due to:
- sulfur impurities in fossil fuel, especially coal
- Volcanic activity

Question 6

State the source of Nitrogen monoxide and nitrogen dioxide

Answer 6

1. Combustion of nitrogen due to high temperatures in internal combustion engine
2. Combustion of energy due to high voltages caused by lightning

Question 7

State the source of unburnt hydrocarbons

Answer 7

Incomplete combustion of carbon-based fuels

Question 8

State the source of methane

Answer 8

1. Bacterial decomposition of organic matter

Question 9

Describe and explain the effects of greenhouse gases

Answer 9

Greenhouse gases trap heat by absorbing infra-red radiation, which in excess leads to global warming, causing:
1. Melting of polar ice caps and hence rising sea levels
2. Drying up of rivers and lakes and hence leading to feast and famine.

Question 10

Describe the carbon cycle

Answer 10

The carbon cycle is a system of chemical and biological reactions that occur to regulate the carbon dioxide levels in our atmosphere, hence regulating the greenhouse effect.

Question 11

Describe and explain the effects of carbon monoxide

Answer 11

Carbon monoxide is poisonous as it binds irreversibly with haemoglobin in our blood, preventing the transport of oxygen in our body, leading to headache, fatigue, and even death

Question 12

Describe and explain the effects of Nitrogen oxides and Sulfur dioxides

(Note: Nitrogen monoxide is neutral while NO2 is acidic. NO dissolves in water to form nitrous acid and HNO3)

Answer 12

Nitrogen oxides and Sulfur dioxide are acidic gases, and hence react with water and oxygen to form strong acids of sulfuric acid and nitric acid, which causes acid rain.
1. Acid rain corrodes limestone and metallic buildings and kills vegetation
2. Acid rain also causes eye irritation and lung damage then they get into contact with our eyes and lungs.

Question 13

Describe and explain the effects of Chloroflurocarbons

Answer 13

Chlorofluorocarbons emit chlorine radicals which catalyse the decomposition of ozone, leading to overexposure to ultra-violet rays on Earth surface, which causes cataract and skin cancer.

Question 14

State the effects of CFC, HCFC, and HFC

Answer 14

CFC - Damages ozone layer, greenhouse gas
HCFC - Damages ozone layer, greenhouse gas
HFC - Greenhouse gas