Texas Wastewater Class B Practice Exam

Which gas is described as greenish-yellow, pungent, and highly toxic?

1. Chlorine

2. Hydrochloric Acid

3. Ammonia

4. Sulfur Dioxide

The correct answer is: Chlorine

The gas that is greenish-yellow, pungent, and highly toxic is indeed chlorine. Chlorine is often recognized by its distinct strong smell, which can be irritating and harmful to the respiratory system. It is widely used in water treatment processes, but because of its toxic nature, exposure to chlorine gas can lead to severe health issues, including respiratory distress and, in high concentrations, can be fatal. The other options present different characteristics and uses. Hydrochloric acid is a strong acid that, when in gaseous form, does not share the same greenish-yellow color or pungent nature associated with chlorine. Ammonia has a sharp, distinct odor but is colorless and differs in toxicity profile. Sulfur dioxide, while also toxic and harmful, is generally colorless, although it can have a slightly pungent odor similar to burnt matches. Understanding the properties and effects of each of these gases is important for safety in handling and working in wastewater treatment environments.