Enthalpy of formation

Question

Using standard heats of formation, calculate the standard enthalpy change for the following reaction.

2H₂O(l)2H₂(g) + O₂(g)

Answer 1

It would help (and be nice) if you would include the standard heats of formation so that we don't have to look them up. So, here's what you do...

Look up ∆Gº_f for H₂(g) and O₂(g) and you should find that they are both zero. Then look up the ∆Hº_f for H₂O(l). Then use products - reactants to find ∆H_rxn, so it will be 0 - ∆Hº_f H2O(l).