Reaction C₂H₅OH + 3O₂ --> 2CO₂ + 3H₂O
Then draw the structural formulas for each molecule showing single and double bonds.
C₂H₅OH has one C-C bond, five C-H bonds, one C-O bond and one O-H bond
add up the bond energies for a mole of each of these single bonds from your bond energy chart.
Now in O₂ we have O=O double bond so add up the total bond
energy for three moles of O₂. (three times the doubly bonded oxygen
CO₂ is formed O=C=O, and you have two moles of CO₂, and four
moles of C=O bonds so multiply the C=O bond energy by 4
and for H₂O, bonded H-O-H you will have 6 moles of H-O bonds, so multiply the H-O bond energy by six.
Now to get ΔH for this reaction, simply subtract the sum of the
reactant bond energies from the sum of the product bond energies and you