Question

according to hesss law, if a series of intermediate reactions are combined, the enthalpy change of the overall reaction is
the difference between the enthalpies of the intermediate reactions.
the sum of the enthalpy changes of the intermediate reactions.
the product of the enthalpy changes of the intermediate reactions.
the fraction of the individual enthalpies of the intermediate reactions.

Explanation:

Hess's law states that the enthalpy change of an overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions (or steps) that make up the overall reaction. This is because enthalpy is a state function, so the path taken (via intermediate reactions) doesn't affect the total enthalpy change, only the sum of the enthalpy changes of each step. The other options (difference, product, fraction) do not align with the definition of Hess's law.

Answer:

the sum of the enthalpy changes of the intermediate reactions.