Florida Drinking Water Operator "B" Practice Test

What color is chlorine gas?

1. Colorless

2. Greenish-yellow

3. Yellow

4. Brown

The correct answer is: Greenish-yellow

Chlorine gas is recognized primarily as being greenish-yellow in color. This distinctive hue is a result of the gas's physical and chemical properties. Chlorine is a diatomic molecule, and when it is in its gaseous state, it can absorb and scatter light in a way that gives it this noticeable greenish-yellow tint. This characteristic color makes chlorine easily identifiable, which is important for safety reasons, especially in water treatment facilities where chlorine is commonly used for disinfection. Additionally, understanding the physical properties of chlorine gas helps operators recognize potential hazards. Since chlorine is toxic and can be harmful in high concentrations, being able to identify its color can be crucial for implementing safety measures and responding quickly to leaks or exposure incidents. Therefore, the greenish-yellow color of chlorine links directly to its application and handling in drinking water treatment processes.