Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

Which of the following describes a physical characteristic of chlorine gas?

1. Colorless and odorless

2. Greenish-yellow color, heavier than air, pungent penetrating odor, corrosive

3. Clear and sweet-smelling

4. Colorful and odorless

The correct answer is: Greenish-yellow color, heavier than air, pungent penetrating odor, corrosive

The choice that accurately describes a physical characteristic of chlorine gas is the one indicating that it is greenish-yellow, heavier than air, has a pungent penetrating odor, and is corrosive. Chlorine gas is indeed a greenish-yellow gas at room temperature and exhibits a distinctive, strong odor that can be described as pungent or irritating. Its density is greater than that of air, which is important to note because it means that chlorine can accumulate in low-lying areas if released into the atmosphere. The corrosive nature of chlorine gas also highlights its potential dangers; it can react with moisture and form hydrochloric acid, which can be harmful to living tissues and materials. Understanding this characteristic is vital for safety practices in environments where chlorine is used, such as in water treatment facilities. Other options inaccurately describe chlorine: for example, it is not colorless and odorless, does not have a "clear and sweet-smelling" profile, nor is it described as "colorful and odorless." Such descriptions do not align with the recognized properties of chlorine gas, which is critical to recognize for practical applications and safety measures.