Enthalpy Reaction from Enthalpy Formation

Question

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

Fe₃O₄(s) + 4H₂(g)3Fe(s) + 4H₂O(g)

Answer 1

Look up in a table (text book, internet, etc.) the standard heats of formation (∆H_formation) for the products and the reactants. Note that ∆H for Fe(s) and for H₂(g) will be zero, so you may not find them in the table.

So, you'll be left with ∆Hf for H₂O(g) and for Fe₃O₄₍s). Multiply the value for H₂O by 4 since there are 4 moles in the balanced equation. Then proceed as follows:

∆Hf products - ∆H products = ∆H_reaction (PAY CAREFUL ATTENTION TO THE SIGNS)