Topic 5.2: Hess's Law Flashcards

1
Q

Hess’s law statement

A

Total enthalpy change in a chemical reaction depends only upon the initial and final states and is independent of the reaction pathway.

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2
Q

Why does Hess’s law work?

A

a) Enthalpy is a property of a substance under a certain set of conditions
b) The route that is taken between A and B cannot affect the amount of enthalpy A or B has
c) Thus, the difference in enthalpy between A and B is constant

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3
Q

Rules for Hess’s law (4)

A

a) The magnitude of ΔH is proportional to the amount of reactant consumed in the process.
b) The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to ∆H for the reverse reaction
c) The enthalpy change for a reaction depends on the states of the reactants and products

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