Use data from Appendix IIB to calculate ΔS°_rxn for each of the reactions. In each case, try to rationalize the sign of ΔS°_rxn. d. N₂O₄(g) + 4 H₂(g) → N₂(g) + 4 H₂O(g)

Verified step by step guidance

1. Identify the standard molar entropy values (S°) for each reactant and product from Appendix IIB.
2. Write the balanced chemical equation: \( \text{N}_2\text{O}_4(g) + 4 \text{H}_2(g) \rightarrow \text{N}_2(g) + 4 \text{H}_2\text{O}(g) \).
3. Calculate the total standard entropy of the products: \( S^\circ_{\text{products}} = S^\circ_{\text{N}_2(g)} + 4 \times S^\circ_{\text{H}_2\text{O}(g)} \).
4. Calculate the total standard entropy of the reactants: \( S^\circ_{\text{reactants}} = S^\circ_{\text{N}_2\text{O}_4(g)} + 4 \times S^\circ_{\text{H}_2(g)} \).
5. Determine the standard entropy change for the reaction: \( \Delta S^\circ_{\text{rxn}} = S^\circ_{\text{products}} - S^\circ_{\text{reactants}} \).

Key Concepts

Entropy (ΔS)

Entropy, represented as ΔS, is a measure of the disorder or randomness in a system. In chemical reactions, changes in entropy can indicate how the arrangement of molecules changes from reactants to products. A positive ΔS suggests an increase in disorder, while a negative ΔS indicates a decrease in disorder.

Standard Entropy of Formation

The standard entropy of formation is the entropy content of a substance in its standard state, typically at 1 bar of pressure and a specified temperature (usually 298 K). This value is crucial for calculating the overall change in entropy for a reaction, as it allows for the comparison of the entropies of reactants and products.

Reaction Stoichiometry

Reaction stoichiometry refers to the quantitative relationships between the amounts of reactants and products in a chemical reaction. Understanding stoichiometry is essential for calculating changes in entropy, as it helps determine how many moles of each substance are involved, which directly affects the overall entropy change (ΔS°rxn) for the reaction.