Which of the following is the mathematical form of Hess's law?

Options

A. `Delta H_(rxn)^(@) = sum n Delta_(f) H^(@)` (products) - `sum n Delta_(f) H^(@)` (reactants)
B. `Delta H_(rxn)^(@) = sum n Delta_(f) H^(@)` (products) `// sum n Delta_(f) H^(@)` (reactants)
C. `Delta H_(rxn)^(@) = sum n Delta_(f) H^(@)` (products) + `sum n Delta_(f) H^(@)` (reactants)
D. All of these

Answer

A

Explanation

The standard enthalpy change of a reaction is equal to the sum of the stantard molar enthalpies of formation of the products, each mulitplied by its coefficient `n` in the balanced equation minus the corresponding sum of the standard molar enthalpies of formation of the reactants.