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Topic Combustion
Asked 6 times across 2 UPSC exams over 23 years (2000–2023), peaking in 2023.
Key insights
- Most tested in CDS — 5 of 6 PYQs
- Most asked in 2023
- Recurs across 5 years (2000–2023)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CSE 2000 → CDS 2014
How the concept evolved
Long-running — most appearances (3 of 6) predate 2016, and it still returns.
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.
CDS2023
Consider the following statements regarding burning of magnesium ribbon in air
- White powder of MgO is formed
- It is an example of combustion reaction
- Heat and light are produced
Which of the statements given above are correct?
- A 1 and 2 only
- B 1 and 3 only
- C 2 and 3 only
- D 1, 2 and 3 ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
CDS2023
Naphthalene burns with a yellow sooty flame. This is because
- A carbon to hydrogen ratio is low
- B there is incomplete combustion ✓
- C there is excess supply of air
- D of presence of impurities of nitrogen and sulfur
✓ Correct answer: (B)
Science & Technology › Physics & Chemistry
CDS2022
While burning hydrocarbon fuels, if we see a yellow flame with lots of black smoke, it means that the fuel is :
- A made of saturated hydrocarbons.
- B made of unsaturated hydrocarbons. ✓
- C burning completely.
- D wet.
✓ Correct answer: (B)
Science & Technology › Physics & Chemistry
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