Question

question 1 of 30
what does hesss law state about the total enthalpy change for a reaction?

a. it must be determined experimentally.

b. it is independent of the reaction pathway.

c. it depends on the reaction pathway.

d. it can only be calculated from the equilibrium constant.

Explanation:

Hess's law states that the total enthalpy change of a chemical reaction is independent of the path taken (i.e., the sequence of steps or intermediate reactions) and depends only on the initial and final states of the reactants and products.

• Option A is incorrect because Hess's law allows calculating enthalpy change without always needing experimental determination (e.g., using known enthalpy changes of other reactions).
• Option C is incorrect as Hess's law says enthalpy change does not depend on the reaction pathway.
• Option D is incorrect because enthalpy change is not calculated from the equilibrium constant; the equilibrium constant relates to the ratio of concentrations/partial pressures at equilibrium, not enthalpy directly.
• Option B matches the definition of Hess's law.

Answer:

B. It is independent of the reaction pathway.