When calculating the heat of reaction using standard enthalpies of formation, what is the formula used?

The correct formula to calculate the heat of reaction using standard enthalpies of formation is represented as the change in standard enthalpy of the reaction equaling the total standard enthalpies of formation of the products minus the total standard enthalpies of formation of the reactants. This relationship is rooted in Hess's law, which states that the total enthalpy change of a reaction is the sum of the enthalpy changes for the individual steps of the reaction, regardless of the pathway taken.

In practice, when you use standard enthalpies of formation to find the enthalpy of a reaction, you first sum the standard enthalpies of formation for all the products involved in the reaction, and then you subtract the sum of the standard enthalpies of formation for all the reactants. This subtraction reflects the energy required to break apart the reactants compared to the energy released when forming the products.

Thus, the mathematical representation correctly captures this relationship, where you take the sum of the standard enthalpies of the products and then deduct the sum of the standard enthalpies of the reactants to yield the overall enthalpy change of the reaction. This method is fundamental in thermochemistry, allowing chemists to predict whether a