Which of the following can reduce decomposition of H₂ O₂ on exposure to light :

Solution

Chemistry ma’am · 3 steps

Three of these options speed up the breakdown of H₂O₂. Only urea slows it down, as a stabiliser.

1. The decomposition. H₂O₂ slowly breaks down on standing, and light makes it faster: 2H₂O₂ → 2H₂O + O₂. Anything that catalyses this reaction makes storage worse.

   Option	Effect on decomposition	Reason
   Urea	Slows it down	Added as a stabiliser (negative catalyst) to stored H₂O₂
   Glass containers	Speeds it up	Glass releases traces of alkali, which catalyse the breakdown
   Alkali	Speeds it up	Alkali directly catalyses the decomposition
   Dust	Speeds it up	Dust particles can set off rapid, even explosive, decomposition

2. How it is stored. That is why H₂O₂ is kept in wax-lined glass or plastic bottles, in the dark, away from dust, with a little urea added.
3. So. Urea is the only option that reduces the decomposition, so the answer is (a).

The idea to keep. For H₂O₂ storage, remember: light, alkali, metal surfaces, plain glass and dust all speed up decomposition. Dark plastic or wax-lined bottles and urea as a stabiliser slow it down.

Answer from the NTA final answer key. Solution by PrepWiser.