The action of zinc on an acid produces

Analyze the question: The question asks what gas or product forms when zinc, a reactive metal, reacts with an acid.

Explain the concept: Metals above hydrogen in the reactivity series displace hydrogen from dilute acids. Zinc is above hydrogen, so it reacts with dilute acids to form a salt and hydrogen gas.

General equation: Metal + Acid → Salt + Hydrogen

Show the solution:

With dilute hydrochloric acid: Zn + 2HCl → ZnCl₂ + H₂↑

With dilute sulphuric acid: Zn + H₂SO₄ → ZnSO₄ + H₂↑

In both cases, the zinc atoms lose electrons and become Zn²⁺ ions. The H⁺ ions from the acid gain those electrons and form hydrogen gas:

Zn → Zn²⁺ + 2e⁻ 2H⁺ + 2e⁻ → H₂

Check the other options:

• A. Chlorine: it is not produced. The chloride stays in the salt as ZnCl₂.
• C. Nitrogen: not formed in this reaction.
• D. Sulphur: not formed with dilute acids. Sulphur-containing products appear only under special conditions with concentrated sulphuric acid.
• E. Water vapour: not the main product here.

Answer: B. hydrogen

Exam tip: Remember "Metal + Acid → Salt + Hydrogen". The test for hydrogen is that it burns with a pop sound when a lighted splint is brought near it. Nitric acid is the exception, because it is a strong oxidizing agent and usually does not give hydrogen. For this question, though, hydrogen is the answer.