JEE Main 2023 · 13 April · evening · Single correct · +4 / −1
What happens when methane undergoes combustion in systems A and B respectively?
- (a) System A | System B; Temperature falls | Temperature rises
System A System B Temperature falls Temperature rises - (b) System A | System B; Temperature rises | Temperature remains same
System A System B Temperature rises Temperature remains same - (c) System A | System B; Temperature falls | Temperature remains same
System A System B Temperature falls Temperature remains same - (d) System A | System B; Temperature remains same | Temperature rises
System A System B Temperature remains same Temperature rises
Answer and solution
Answer (b) System A | System B; Temperature rises | Temperature remains same
Solution
Chemistry ma’am · 4 steps
Combustion releases heat; ask where that heat can go: trapped in A, leaking out through the walls of B.
- Combustion is exothermic. Burning methane, CH₄ + 2O₂ → CO₂ + 2H₂O, releases heat. What happens to the temperature depends on whether the walls let that heat out.
System Walls Heat exchange Temperature A Adiabatic None, q = 0; heat stays inside Rises B Diathermic Heat flows out to the surroundings Remains same - System A. Adiabatic walls block heat flow. The energy released by combustion stays inside and warms the products, so the temperature rises.
- System B. Diathermic walls conduct heat. The released heat passes out to the surroundings until the system is back at their temperature, so its temperature stays the same.
- So. Temperature rises in A and remains the same in B, which is option (b).
The idea to keep. Adiabatic walls trap heat, so an exothermic change heats the system. Diathermic walls pass heat out, so the system stays at the temperature of its surroundings.
Answer from the NTA final answer key. Solution by PrepWiser.