Which of the following is an endothermic reaction?
A. Reaction of sodium with water
B. Respiration
C. Burning of natural gas
D. Decomposition of calcium carbonate
Answer: Option D
Solution (By JKSSB Mock Tests)
Endothermic reactions absorb heat from the surroundings. The decomposition of calcium carbonate (CaCO₃ → CaO + CO₂) requires continuous heating to proceed. Burning of gas, respiration, and the reaction of sodium with water are all exothermic reactions that release significant amounts of heat energy to the surroundings.
Explanation:
Niels Bohr proposed his model in 1913 to overcome the defects of Rutherford's model. He stated that electrons revolve around the nucleus in specific, discrete circular orbits (shells) with fixed energy, and they do not radiate energy while in these orbits, explaining atomic stability.
Explanation:
Hydrogenation is the addition of hydrogen to unsaturated compounds (like alkenes or alkynes) in the presence of a catalyst (like Ni, Pd, or Pt) to form saturated compounds (alkanes). For example, ethene + H₂ → ethane. This process is widely used in the food industry to solidify vegetable oils.
Explanation:
Vulcanization is the chemical process of converting natural rubber or related polymers into more durable materials by adding sulfur or other equivalent curatives. This process was discovered by Charles Goodyear in 1839, revolutionizing the rubber industry by making it less sticky and more temperature-resistant.
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