Use standard enthalpies of formation to calculate ΔH°rxn for the reaction: CO(g) + H2O(g) → H2(g) + CO2(g)

Verified step by step guidance

1. Identify the standard enthalpy of formation (ΔH°f) for each compound involved in the reaction: CO(g), H2O(g), H2(g), and CO2(g). These values are typically found in a table of standard enthalpies of formation.
2. Write the balanced chemical equation for the reaction: CO(g) + H2O(g) → H2(g) + CO2(g).
3. Apply the formula for calculating the standard enthalpy change of the reaction (ΔH°rxn): ΔH°rxn = Σ(ΔH°f of products) - Σ(ΔH°f of reactants).
4. Substitute the standard enthalpy of formation values into the formula: ΔH°rxn = [ΔH°f(H2) + ΔH°f(CO2)] - [ΔH°f(CO) + ΔH°f(H2O)].
5. Calculate the sum of the enthalpies of formation for the products and the reactants separately, then subtract the sum for the reactants from the sum for the products to find ΔH°rxn.

Key Concepts

Enthalpy of Formation

The standard enthalpy of formation (ΔH°f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. It is a crucial value used in thermodynamics to calculate the heat changes in chemical reactions. Each substance has a specific ΔH°f value, which is typically found in tables and is essential for determining the overall enthalpy change of a reaction.

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same, regardless of the number of steps taken to achieve the reaction. This principle allows for the calculation of ΔH°rxn by summing the enthalpy changes of individual steps or reactions. It is particularly useful when direct measurement of a reaction's enthalpy change is difficult or impossible.

Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. It is essential for balancing chemical equations and determining the amounts of substances consumed and produced. In the context of calculating ΔH°rxn, stoichiometry ensures that the enthalpy values used correspond to the correct molar ratios of the reactants and products involved in the reaction.