Heat of change in a chemical reaction is the same whether it takes place in one or indirectly in several steps. This represents:
Correct answer: C. Hess's Law.
- A. First law of thermodynamics.
- B. Law of conservation of energy.
- C. Hess's Law.
- D. None of the above
Explanation
The correct answer is Hess's Law. Hess's Law states that the total enthalpy change for a chemical reaction is the same, regardless of whether it occurs in a single step or multiple steps. This principle allows us to calculate reaction enthalpies using known enthalpies of formation or other reactions. The First Law of Thermodynamics and the Law of Conservation of Energy relate to the overall energy balance in a system, but they do not specifically address the enthalpy changes in stepwise reactions. Therefore, these options are incorrect in the context of this question.
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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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