The given reaction is:
H2(g) + CO2(g) → H2O(g) + CO(g)
i.e.
H-H + O=C=O → H-O-H + C≡O
Reaction enthalpy (ΔH) is given as:
ΔH = ∑ΔH(Bonds broken) + ∑ΔH(Bonds formed)
= [1*ΔH(H-H) + 2*ΔH(C=O)] + [2*ΔH(O-H) + 1*ΔH(C≡O)]
=[+436 +2(799)] + [2(-463) +1(-1072)] = 36 kJ/mol
The enthalpy change for the given reaction is 36 kJ/mol
