Which gas is described as pale green with a choking smell and is poisonous?

• A. Chlorine
• B. Oxygen
• C. Hydrogen
• D. Carbon Dioxide

Answer: (A)

Chlorine gas fits this description. It is a pale green gas with a very sharp, choking odor and is highly poisonous. Its irritant nature comes from reacting with moisture in the air and in your airways to form acids that damage tissues, causing coughing, burning eyes, and breathing difficulties. The other gases listed are either colorless or lack that strong choking smell, so they don’t match the description. Oxygen and hydrogen are colorless and odorless, while carbon dioxide is also colorless and odorless but not choking.