The heat of a reaction can be calculated by using:
Correct answer: C. Hess's Law
- A. Joule's Law
- B. Ohm's Law
- C. Hess's Law
- D. Faraday's Law
- E. Boyle's Law
Explanation
Hess' law states that the change of enthalpy in a chemical reaction (i.e. the heat of reaction at constant pressure) is independent of the pathway between the initial and final states. In other words, if a chemical change takes place by several different routes, the overall enthalpy change is the same, regardless of the route by which the chemical change occurs (provided the initial and final conditions are the same). Hess's law allows the enthalpy change (ΔH) for a reaction to be calculated even when it cannot be measured directly.
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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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