Which gas is represented by the formula H₂S?

The formula H₂S represents Hydrogen Sulfide, which is a colorless gas known for its characteristic rotten egg odor. It consists of two hydrogen atoms bonded to one sulfur atom. Hydrogen Sulfide is significant in both environmental and industrial contexts, especially in wastewater treatment, where it can be a byproduct of anaerobic decomposition. Understanding this gas is crucial for wastewater professionals to manage its presence, as it can pose safety hazards and affect water quality.

The other gases listed do not correspond to the formula H₂S. Helium Sulfide, for instance, would imply a combination of helium and sulfur, which is not a common gas and has no established formula. Hydrochloric Sulfide does not exist as a recognized compound; hydrochloric acid (HCl) is a separate entity and does not incorporate sulfur. Sulfur Dioxide (SO₂) is also a distinct chemical compound and does not relate to the original formula of H₂S. Thus, recognizing that H₂S uniquely corresponds to Hydrogen Sulfide is essential for understanding its chemical identity and relevance in wastewater treatment scenarios.