Which gas is produced when water reacts with calcium?

Question

Which gas is produced when water reacts with calcium?

1. A. Hydrogen (Correct answer)
2. B. Oxygen
3. C. Carbon dioxide
4. D. Nitrogen

Correct Answer

Option A — Hydrogen

Detailed Solution & Explanation

The correct answer is Hydrogen.

Key Points

• Calcium is a reactive alkaline-earth metal that reacts with water to form calcium hydroxide and release hydrogen gas:
• Ca + 2H₂O → Ca(OH)₂ + H₂↑.
• The reaction is less violent than that of sodium or potassium, so the hydrogen does not usually catch fire, and the calcium hydroxide formed makes the solution alkaline (lime water).
• metals above hydrogen in the reactivity series displace hydrogen from water or acids.
• Reactive metals such as sodium, potassium and calcium react with cold water to give the metal hydroxide plus hydrogen gas.

Exam Tip

• the general pattern metal + water → metal hydroxide + hydrogen is heavily tested.
• Note the order of vigour: potassium and sodium react explosively, calcium moderately, and magnesium only with hot water or steam.