A metal 'M' on reacting with dilute acid liberates a gas 'G'. The same metal also liberates gas 'G' when reacts with a base.
Generated by claude-sonnet-4-6 · 2026-06-15 06:50 · grounding rag
Model Answer
(i) Gas 'G' is Hydrogen (H₂).
(ii) Bring a burning matchstick near the mouth of the test tube. If the gas burns with a 'pop' sound, it confirms the presence of hydrogen gas.
(iii) Metal 'M' is Zinc (Zn) (reacts with both dilute acid and base to liberate H₂).
(1) Reaction with acid (dilute H₂SO₄):
$$\text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2\uparrow$$
(2) Reaction with base (NaOH):
$$\text{Zn} + 2\text{NaOH} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2\uparrow$$
Source: Metals and Non-metals, Chapter 3, Section 3.2.3
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Explanation
- The key clue is that metal M reacts with both dilute acid and a base to give H₂ — this is a property of amphoteric metals like Zinc (or Aluminium). Zinc is the standard NCERT example.
- The pop test is the standard CBSE test for hydrogen gas — must be stated exactly this way.
- In the base reaction, the salt formed is sodium zincate (Na₂ZnO₂) — a negative ion composed of the metal and oxygen, as described in the chapter.
- Examiners award 1 mark each for (i) name of gas, (ii) test, and (iii) two equations. Write both equations balanced with state symbols (↑ for gas) for full credit.