Question

Hess’s Law states that _______.

A. the enthalpy of a given substance is independent of the way it was made
B. the enthalpy of a given substance depends on the way it was made
C. ΔH is the change in entropy that occurs in a chemical reaction
D. ΔHo = Σ ΔHfo (reactants) – Σ ΔHfo (products)
E. None of the Above

Answer 1

Question # 78485, Chemistry / General Chemistry

Hess's Law states that _______.

A. the enthalpy of a given substance is independent of the way it was made

B. the enthalpy of a given substance depends on the way it was made

C. $\Delta H$ is the change in entropy that occurs in a chemical reaction

D. $\Delta H_0 = \sum \Delta H_{fo}$ (reactants) – $\sum \Delta H_{fo}$ (products)

E. None of the Above

Solution: The law states that the total enthalpy change during the complete course of a chemical reaction is the same whether the reaction is made in one step or in several steps. Hess's law states that enthalpy changes are additive. Thus the $\Delta H$ for a single reaction

$$\Delta H_0 = \sum \Delta H_{fo} \text{ (products)} - \sum \Delta H_{fo} \text{ (reactants)}$$

Answer: A

Source: https://en.wikipedia.org/wiki/Hess%27s_law

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