MCQ Detailed View

Air is not a single substance but a physical mixture of different gases. The major component of air is nitrogen (about 78%), followed by oxygen (about 21%). The remaining part is made up of argon, carbon dioxide, water vapor, neon, helium, and other trace gases. Since these gases are not chemically bonded but only physically mixed, air is classified as a mixture, not a compound.

A compound is formed when two or more elements combine chemically in fixed proportions, such as water (H₂O) or carbon dioxide (CO₂). Air does not meet this definition because its gases can vary in proportion depending on the environment. For example, oxygen levels may be slightly lower in polluted areas, while water vapor levels change with humidity.

An element is a pure substance made of only one type of atom, such as oxygen (O₂) or nitrogen (N₂). Since air contains many different substances together, it cannot be classified as an element.

An electrolyte refers to a substance that produces ions when dissolved in water and conducts electricity, such as sodium chloride (NaCl). Air does not behave in this way, so it is not an electrolyte.

The correct classification of air is a homogeneous mixture because the gases are uniformly distributed and cannot be separated easily by physical observation. However, separation techniques like fractional distillation of liquid air can be used to isolate its components. This property makes air very important in industrial processes such as oxygen production, nitrogen supply, and carbon dioxide capture.

Therefore, in environmental chemistry, air is studied as a mixture of gases that supports life and plays a critical role in the Earth’s atmosphere and ecosystems.