This is the question:
When ethanol burns in oxygen under standard conditions, carbon dioxide, water and 1368 kJmol-1 of energy are produced. Calculate the enthalpy of formation of ethanol, given that the enthalpies of formation of carbon dioxide and water are -393.7 and -285.9 kJmol-1 respectively.
Im confused as first I worked out the sum of the products and i got an answer of -1645.1kJmol-1. Im not able to figure out what the enthalpy of formation of the reactants would be as from the equation it needs to total to 1368 kJmol-1