The constituent of air that acts as a diluent is

Analysis

The question asks for the component of air that functions as a "diluent." In chemistry, a diluent is a substance used to reduce the concentration or reactivity of another substance.

Concept Explanation

Air is a mixture of gases, primarily nitrogen (about 78%) and oxygen (about 21%), with small amounts of argon, carbon (IV) oxide, and water vapor.

Oxygen is highly reactive and supports combustion. If the atmosphere were composed entirely of pure oxygen, fires would be uncontrollable, and the rate of oxidation in living organisms would be dangerously high. Nitrogen serves as an inert (unreactive) buffer that "dilutes" the oxygen, slowing down combustion and making the environment safe for life and controlled burning.

Step-by-Step Solution

1. Identify the roles of the gases: • Oxygen: Essential for respiration and combustion (the active component). • Carbon (IV) oxide: Present in small quantities; used by plants for photosynthesis. • Noble gases: Chemically inert but present in very small quantities. • Nitrogen: Makes up the vast majority of the air. Because it is chemically inactive (inert) under normal conditions, it does not participate in combustion or respiration.
2. Determine the function: Since nitrogen is inert and makes up the largest volume of air, it effectively reduces the concentration of oxygen, thereby acting as a diluent.
3. Conclusion: Nitrogen prevents the rapid combustion of materials and regulates the rate of respiration by diluting the oxygen in the atmosphere.

Correct Answer

The correct option is A.

Exam Tip

Think of nitrogen as the "brake" for oxygen. Without nitrogen, every spark would result in a massive explosion. Remember: Nitrogen = Inert Diluent.