∆H,-572kJ/mol-1 for water It means that:
Correct answer: D. Water is at lower energy than its reactants
- A. It is an endothermic process
- B. Formation of water is a spontaneous process
- C. It is the heat evolved for complete reaction of 2 moles of oxygen with excess of hydrogen
- D. Water is at lower energy than its reactants
Explanation
The correct answer is that water is at lower energy than its reactants. This is supported by the negative enthalpy change (∆H = -572 kJ/mol), indicating that the reaction is exothermic, meaning energy is released when water is formed. This implies that the products (water) have lower potential energy compared to the reactants (hydrogen and oxygen).The other options are incorrect for the following reasons:The first option asserts that the process is endothermic, which contradicts the given negative enthalpy value.The second option discusses spontaneity, which is relevant but does not directly explain the relationship shown by the enthalpy change.The third option misinterprets the reaction stoichiometry; the enthalpy change refers to the formation of water, not specifically to the reaction of two moles of oxygen.
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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