Final answer:
The change in internal energy for the reaction of aragonite to calcite is an endothermic reaction. The correct answer is B.
Step-by-step explanation:
The change in internal energy for the reaction of aragonite to calcite can be classified as an endothermic reaction. Endothermic reactions absorb energy from the surroundings as the reaction occurs. In this specific reaction, when aragonite decomposes into calcite, heat is absorbed, indicating an endothermic reaction. The heat absorbed is written as a reactant in the thermochemical equation.
The change in internal energy for the reaction of aragonite to calcite can be understood by considering the nature of endothermic and exothermic reactions. An endothermic reaction is one where energy is absorbed from the surroundings during the reaction process, such as when 1 mol of calcium carbonate decomposes into 1 mol of calcium oxide and 1 mol of carbon dioxide, absorbing 177.8 kJ of heat. The energy is written as a reactant in the chemical equation, and the enthalpy change (ΔH) is positive, indicating that the system gains energy.
Conversely, an exothermic reaction is one that releases energy into the surroundings, characterized by energy being a product, and ΔH is negative, showing that the system loses energy. Since the reaction of aragonite to calcite is not typically associated with a significant heat transfer, neither exothermic nor endothermic adequately describes it; it is closer to an isothermal process where the temperature remains constant. The correct answer is B.