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Ch.9 - Chemical Bonding I: The Lewis Model
Tro - Chemistry: A Molecular Approach 4th Edition
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Tutti i libri di testoTro 4th EditionCh.9 - Chemical Bonding I: The Lewis ModelProblema 83
Capitolo 9, Problema 83

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.

Concetti chiave

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Bond Energies

Bond energies refer to the amount of energy required to break a bond between two atoms in a molecule. In chemical reactions, the total energy of bonds broken in the reactants is compared to the total energy of bonds formed in the products. This difference in energy is crucial for calculating the enthalpy change (ΔH) of a reaction.
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Bond Energy

Enthalpy Change (ΔH)

Enthalpy change (ΔH) is a measure of the heat absorbed or released during a chemical reaction at constant pressure. It can be calculated using the formula ΔH = Σ(bond energies of reactants) - Σ(bond energies of products). A negative ΔH indicates an exothermic reaction, while a positive ΔH indicates an endothermic reaction.
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Enthalpy of Formation

Stoichiometry of the Reaction

Stoichiometry involves the quantitative relationships between the reactants and products in a chemical reaction. In the given reaction, the coefficients indicate the molar ratios of carbon, water, hydrogen, and carbon dioxide. Understanding stoichiometry is essential for accurately calculating the total bond energies involved and thus determining the ΔHrxn.
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Stoichiometry Concept
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