Question: how to figure out standard enthalpy change of a reaction?
Answer: The following equation can be used to calculate the standard enthalpy of reaction: ΔH⊖rxn=∑ΔH⊖f{products}−∑ΔH⊖f{reactants} Δ H r x n ⊖ = ∑ Δ H f ⊖ { products } − ∑ Δ H f ⊖ { reactants } . The enthalpy of reaction is calculated under standard conditions (STP).