Hydrogen, a potential future fuel, can be produced from carbon (from coal) and steam by this reaction: C(s) + 2 H2O(g) -> H2(g) + CO2(g). Use average bond energies to calculate ΔHrxn for the reaction.

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Identify the bonds broken and formed in the reaction. In the reactants, you have C(s) and 2 H2O(g). In the products, you have H2(g) and CO2(g).

Calculate the total energy required to break the bonds in the reactants. For 2 H2O, you need to break 2 O-H bonds per molecule, totaling 4 O-H bonds.

Calculate the total energy released when new bonds are formed in the products. In H2, you form one H-H bond, and in CO2, you form two C=O bonds.

Use the bond energies to find the energy change: ΔHrxn = (Energy required to break bonds) - (Energy released from forming bonds).

Substitute the average bond energies into the equation and solve for ΔHrxn.

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