In the characteristic reaction method, if the insoluble solid is a metal reacting with an acid, what are the products?

• A. Metal salt and hydrogen
• B. Metal salt and oxygen
• C. Metal salt and water
• D. Hydrogen gas and water

Answer: (A)

When a metal reacts with an acid, the metal undergoes a single-displacement reaction where it dissolves as a metal ion and the hydrogen ions from the acid are reduced to hydrogen gas. The solid metal loses electrons and becomes a positively charged ion in solution, while the acid’s H+ ions gain electrons to form H2 gas that bubbles off. The other part of the product is a metal salt, formed from the metal ion and the anion from the acid. The exact salt depends on the acid used: with hydrochloric acid you get a metal chloride; with sulfuric acid you get a metal sulfate, and so on. For example, zinc reacting with hydrochloric acid yields zinc chloride and hydrogen gas: Zn + 2HCl → ZnCl2 + H2.