Which substance is characterized by reacting with zinc to produce hydrogen gas?

• A. Base
• B. Water
• C. Acid
• D. Salt

Answer: (C)

This question tests how metals interact with acids to release hydrogen gas. When a metal like zinc is placed in an acid, the metal displaces hydrogen from the acid, forming a salt and hydrogen gas. For example, zinc reacts with hydrochloric acid to make zinc chloride and hydrogen gas: Zn + 2HCl → ZnCl2 + H2. This shows why acids are the substance that characteristically produce hydrogen gas with zinc.

Bases, water, and salts don’t provide the same hydrogen-displacement reaction in this standard context. Bases don’t supply hydrogen that can be displaced by zinc to form H2, and while water can react with some metals under certain conditions, zinc and cold water don’t reliably release hydrogen gas in ordinary situations. Salts don’t typically react with zinc to generate hydrogen gas either.