Question

which statement about enthalpy is true?
the enthalpy of formation for a pure element in its standard state is always positive.
the enthalpy of formation for a pure element in its standard state is always negative.
enthalpy is a state function because its change depends only on initial and final conditions.
enthalpy is not a state function because its change depends on the identities of the reactants and p

Explanation:

1. Recall the definition of enthalpy of formation for a pure element in its standard state: It is defined as 0 (neither positive nor negative), so the first two options are incorrect.
2. Recall the definition of a state function: A state function's change depends only on the initial and final states (conditions), not the path taken. Enthalpy (H) is a state function, and its change (ΔH) depends only on initial and final conditions. The fourth option is incorrect as it misstates enthalpy not being a state function. The third option correctly states that enthalpy is a state function because its change depends only on initial and final conditions.

Answer:

Enthalpy is a state function because its change depends only on initial and final conditions.