Environmental chemistry and the air we breathe

What is in one breath?

Every breath you take is mostly a gas your body does not use at all. So which gas is it, and what makes up the rest of the air?

Environmental chemistry studies chemicals and other pollutants in the environment and their harmful effects on living and non-living things. It is part of environmental education, which aims to make people, especially students, aware of protecting and conserving the environment.

Earth is wrapped in a blanket of air called the atmosphere, made of several layers of gases. Animals need it to breathe and plants need it to make food. It contains more nitrogen than any other gas.

By volume (Table 10.1), the major parts are nitrogen 78.0% and oxygen 21.0%. The minor parts are noble gases about 1.0% (mostly argon, 0.934%), carbon dioxide 0.04%, and water vapour, which varies with humidity.

Clean, dry air: about 78% nitrogen, 21% oxygen, and the rest mainly noble gases and carbon dioxide.

Key terms

Environmental chemistry

Understanding pollution.

Atmosphere

Breathing, plant food.

Major constituent

Table 10.1.

Humidity

Why water vapour varies.

Short questions with model answers

1. Q1. What share of clean, dry air is not nitrogen or oxygen?

   • 78.0% + 21.0% = 99.0%
   • 100% − 99.0% = 1.0%

   About 1%, mostly argon and other noble gases, plus 0.04% carbon dioxide.

2. Q2. What is the main objective of environmental education? (Short question i, p. 143)

   • Who
   • What

   To make people, especially students, aware of the importance of protecting and conserving the environment.

Common mistakes

• ✗ Air is mostly oxygen.

  ✓ It is mostly nitrogen: 78.0% against 21.0% oxygen (Table 10.1).

• ✗ Carbon dioxide is a major part of the air.

  ✓ It is a minor constituent, only 0.04%.

• ✗ Water vapour is always the same share of the air.

  ✓ It varies with humidity (Table 10.1).

MCQs

1. 1. Which gas makes up the largest share of the air?

   1. (a) Oxygen
   2. (b) Nitrogen
   3. (c) Argon
   4. (d) Carbon dioxide
   Show answer

   (b) 78.0% (Table 10.1).

2. 2. What percentage of air is carbon dioxide?

   1. (a) 0.04%
   2. (b) 0.934%
   3. (c) 1.0%
   4. (d) 21.0%
   Show answer

   (a) Table 10.1.

3. 3. Which gas is released when a carbonated drink is opened? (Exercise 2, p. 131)

   1. (a) Oxygen
   2. (b) Nitrogen
   3. (c) Carbon dioxide
   4. (d) Argon
   Show answer

   (c) Carbonated means CO₂ is dissolved in it.

4. 4. Which constituent of the air changes with humidity?

   1. (a) Nitrogen
   2. (b) Argon
   3. (c) Water vapour
   4. (d) Oxygen
   Show answer

   (c) Table 10.1.

5. 5. Which noble gas is the largest part of the air?

   1. (a) Helium
   2. (b) Neon
   3. (c) Argon
   4. (d) Radon
   Show answer

   (c) 0.934% of about 1.0% (Table 10.1).

Quick revision

• Environmental chemistry studies chemicals and pollutants in the environment and their effects.
• Air is about 78% nitrogen and 21% oxygen.
• Minor parts: noble gases (about 1%), carbon dioxide (0.04%) and variable water vapour.