ACS Chemistry Practice Exam 2025 – The All-in-One Guide to Exam Success!

Hydrochloric acid is identified by the chemical formula HCl. This strong acid consists of hydrogen and chlorine, and it forms when hydrogen chloride gas dissolves in water. Hydrochloric acid is widely used in various applications, including cleaning, food processing, and chemical synthesis, due to its ability to donate protons (H⁺ ions) and its corrosive nature.

In contrast, other options represent different acids:

- HClO4 is known as perchloric acid, which contains an additional oxygen atom and is a much stronger acid than hydrochloric acid.

- H2SO4 is sulfuric acid, a diprotic acid with significant industrial and laboratory applications, but is entirely different from hydrochloric acid in both composition and behavior.

- HBr stands for hydrobromic acid, which is comparable to hydrochloric acid but contains bromine instead of chlorine.

Thus, the designation of hydrochloric acid specifically refers to HCl, making it clear that B is the correct answer.