Calculez à 298 K, l'enthalpie de la réaction de synthèse du...

Calculez à $298 \mathrm{~K}$, l'enthalpie de la réaction de synthèse du méthanol dont l'équation stœchiométrique s'écrit : $$ \mathrm{CO}(\mathrm{g})+2 \mathrm{H}_2(\mathrm{~g})=\mathrm{CH}_3 \mathrm{OH} \text { (1) } $$ a) à partir des enthalpies de formation ; b) à partir des énergies de liaison.

Calculez à $298 \mathrm{~K}$, l'enthalpie de la réaction de synthèse du méthanol dont l'équation stœchiométrique s'écrit :
$$
\mathrm{CO}(\mathrm{g})+2 \mathrm{H}_2(\mathrm{~g})=\mathrm{CH}_3 \mathrm{OH} \text { (1) }
$$
a) à partir des enthalpies de formation ;
b) à partir des énergies de liaison.

Key Concepts

Enthalpy of Formation

This concept refers to the heat change that accompanies the formation of one mole of a compound from its constituent elements in their standard states. It is a fundamental quantity in thermochemistry used as a reference to calculate the overall reaction enthalpy by comparing the energies required to form versus decompose compounds.

Hess's Law

Hess's Law states that the total enthalpy change for a chemical reaction is the same regardless of the number of intermediate steps. This allows the calculation of a reaction's enthalpy by summing the standard enthalpies of formation of products and subtracting those of the reactants, irrespective of the reaction pathway.

Bond Energy

The bond energy method computes reaction enthalpy based on the energy required to break chemical bonds in reactants (an endothermic process) and the energy released when new bonds form in products (an exothermic process). This approach provides an alternative way to assess the energetics of a reaction by considering individual bond contributions.

Stoichiometry

Stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. In the context of thermochemistry, it ensures that the calculated enthalpy changes are correctly scaled according to the balanced chemical equation, taking into account the proportion of moles of substances involved.

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