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Q12
(CAPF/2021)
Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles
Answer Verified
Which one of the following is an example of endothermic reaction?
A) CaO(s) + H₂O(l) → Ca(OH)₂(aq)
B) CaCO₃(s) → CaO(s) + CO₂(g)
C) C(s) + O₂(g) → CO₂(g)
D) CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)
Result
Your answer:
—
·
Correct:
B
Explanation
An endothermic reaction is one that absorbs heat energy from the surroundings. The decomposition of calcium carbonate (CaCO₃) into calcium oxide (CaO) and carbon dioxide (CO₂) requires high temperatures to proceed, making it a thermal decomposition reaction, which is endothermic.
- Option A: The reaction of quicklime (CaO) with water is highly exothermic, releasing significant heat.
- Option B: Thermal decomposition of CaCO₃ absorbs energy, identifying it as endothermic.
- Options C and D: Combustion reactions (burning carbon or methane) are always exothermic as they release energy.
Therefore, Option B is the correct choice as it represents the absorption of thermal energy (ΔH > 0).
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