## Using the standard enthalpies of formation, what is the standard enthalpy of reaction?

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1. Using the standard enthalpies of formation, what is the standard enthalpy of reaction?
CO(g)+H2O(g) ⇋⇋ CO2(g)+H2(g).
Reaction Enthalpy:
The overall energy change in a reaction is equal to the reaction enthalpy. It is equal to the total standard enthalpies of formation of the products minus the total standard enthalpies of formation of the reactants. The sign of the reaction enthalpy indicates the type of reaction. If it is negative, overall heatis released in the reaction and the reaction is said to be exothermic. If it is positive, heat is absorbed in the overall reaction and the reaction is said to be endothermic.
Answer and Explanation:
The standard enthalpies of formation of the involved gaseous species, from the thermodynamic table, are:
ΔH0f(H2)=0
ΔH0f(CO)=−110.5kJ/mol
ΔHf(CO2)0=−393.5kJ/mol[MathJaxfullWidth=′false′ΔH=(0+(−393.5)−(−110.5)−241.8)k
ΔH0f(H2O)=241.8kJ/mol
The enthalpy change of a reaction is equal to total enthalpy of formation of products minus the total enthalpy of formation of reactants.
Thus, for the given reaction:
ΔH=ΔH0f(H2)+ΔH0f(CO2)−ΔH0f(CO)−ΔH0f(H2O)
⇒ΔH=−524.8kJ/mol

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