Question

question 3 of 30
what is the best definition of the enthalpy of formation, $\delta h_f$?

a. the energy absorbed when products form in a reaction

b. the energy released when products form in a reaction

c. the energy required for an atom to form from its subatomic particles

d. the energy required for a molecule to form from its elements

Explanation:

To determine the best definition of enthalpy of formation ($\Delta H_f$), we analyze each option:

• Option A: Enthalpy of formation isn’t just about energy absorbed (it can be released too, depending on the reaction). Eliminate A.
• Option B: Similarly, it isn’t only about energy released (some formations absorb energy). Eliminate B.
• Option C: Enthalpy of formation relates to molecules forming from elements, not atoms from subatomic particles (that’s a different concept, like binding energy). Eliminate C.
• Option D: The enthalpy of formation is defined as the energy change (required or released) when 1 mole of a compound is formed from its constituent elements in their standard states. This matches the core definition.

Answer:

D. The energy required for a molecule to form from its elements