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Topic Decomposition reaction
Asked 4 times across 2 UPSC exams over 2 years (2021–2023), peaking in 2023.
Key insights
- Most tested in NDA — 3 of 4 PYQs
- Most asked in 2023
- Recurs across 3 years (2021–2023)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
GEO 2021 → NDA 2022
How the concept evolved
Rising — more than half its appearances (4 of 4) are since 2016.
Related concepts
Ideas UPSC tests alongside this one — keep exploring.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
NDA2023
Match List I with List II and select the correct answer using the code given below the Lists
| List I (Chemical process) | List II (Reaction) |
|---|
| A. Electrolysis of water | 1. Double displacement reaction |
| B. Burning of coal | 2. Combination reaction |
| C. Iron nail immersed in copper sulphate solution | 3. Decomposition reaction |
| D. Addition of barium chloride solution to aluminium sulphate solution | 4. Displacement reaction |
Codes:
- A A-3 B-4 C-2 D-1
- B A-4 B-2 C-1 D-3
- C A-3 B-2 C-4 D-1 ✓
- D A-4 B-1 C-2 D-3
✓ Correct answer: (C)
Science & Technology › Physics & Chemistry
NDA2023
Consider the following reaction : 2HgO → 2Hg + O2 The respective state of HgO, Hg and O2 in the above reaction is
- A Liquid, solid, gas
- B Solid, solid, gas
- C Liquid, solid, liquid
- D Solid, liquid, gas ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
NDA2022
Which one of the following reactions is an example of decomposition reaction?
- A CH4(g) + 2O2(g) -> CO2(g) + 2H2O(g)
- B 2AgCl(s) --sunlight--> 2Ag(s) + Cl2(g) ✓
- C CuO + H2 --Heat--> Cu + H2O
- D Fe(s) + CuSO4(aq) -> FeSO4(aq) + Cu(s)
✓ Correct answer: (B)
Science & Technology › Physics & Chemistry
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