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Q4 (NDA-I/2012) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles Answer Verified

Statement I: At high temperature, hydrogen can reduce PbO to elemental lead. Statement II : Hydrogen has great affinity to oxygen

Result
Your answer: —  Â·  Correct: A
Explanation

Statement I is true as hydrogen acts as a reducing agent for metal oxides. At high temperatures (typically 350–800 °C), hydrogen gas reacts with lead(II) oxide (PbO) to produce elemental lead (Pb) and water vapor [1]. This is a classic redox reaction where PbO loses oxygen (reduction) and hydrogen gains oxygen (oxidation) [1]. Statement II is also true; hydrogen has a high affinity for oxygen, which is the fundamental chemical driver for its role as a reducing agent. In the reactivity series, although lead is often placed near hydrogen, the high affinity of hydrogen for oxygen at elevated temperatures allows it to displace lead from its oxide. Since this affinity is the reason hydrogen can strip oxygen from PbO to form water, Statement II provides the correct chemical explanation for the reduction described in Statement I.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > CuO +H Cu+H O 2 2 → Heat (1.29) > p. 12
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