Hydrogen gas, a potential fuel of the future, can be made by the reaction of methane gas and steam.

CH $_{4}(g) + 2 H_{2}O(g) →4 H_{2}(g) + CO_{2}$ (g)

Use bond energies to calculate ∆H $_{rxn}$ for this reaction.

Question

Hydrogen gas, a potential fuel of the future, can be made by the reaction of methane gas and steam.

CH[latex]_{4}(g) + 2 H_{2}O(g) →4 H_{2}(g) + CO_{2}[/latex](g)

Use bond energies to calculate ∆H[latex]_{rxn}[/latex] for this reaction.

Accepted Answer

Begin by rewriting the reaction using the Lewis structures of the molecules involved
Determine which bonds are broken in the reaction and sum the bond energies of these.	Σ(∆H’s bonds broken) = 4(C—H) + 4(O—H) = 4(414 kJ) + 4(464 kJ) = 3512 kJ
Determine which bonds are formed in the reaction and sum the negatives of the bond energies of these.	Σ(∆H’s bonds formed) = -4(H—H) - 2(C=O) = -4(436 kJ) - 2(799 kJ) = -3342 kJ
Find ∆H[latex]_{rxn}[/latex]by summing the results of the previous two steps.	∆H[latex]_{rxn}[/latex] = Σ(∆H’s bonds broken) + Σ(∆H’s bonds formed) = 3512 kJ - 3342 kJ = 1.70 × 10² kJ

Question 9.11: Hydrogen gas, a potential fuel of the future, can be made by...