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. c. SO₂(g) + 1/2 O₂(g) → SO₃(g)

Verified step by step guidance

1. Identify the standard molar entropy (S°) values for each reactant and product from Appendix IIB. You will need the values for SO2(g), O2(g), and SO3(g).
2. Write the balanced chemical equation, which is already given: SO2(g) + \(\frac{1}{2}\)O2(g) → SO3(g).
3. Calculate the total entropy of the reactants by multiplying the molar entropy of each reactant by its stoichiometric coefficient and then summing these values. For the reactants, it will be: S°(SO2) + \(\frac{1}{2}\)S°(O2).
4. Calculate the total entropy of the products similarly. Since there is only one product, SO3(g), this step involves just taking the molar entropy of SO3.
5. Determine ΔS°rxn by subtracting the total entropy of the reactants from the total entropy of the products: ΔS°rxn = S°(SO3) - [S°(SO2) + \(\frac{1}{2}\)S°(O2)]. Rationalize the sign of ΔS°rxn based on the number of gas molecules in the reactants and products; fewer gas molecules in the products typically suggest a decrease in entropy.

Key Concepts

Entropy (ΔS)

Entropy is a measure of the disorder or randomness in a system. In chemical reactions, changes in entropy (ΔS) indicate how the distribution of energy and matter changes as reactants transform into products. A positive ΔS suggests an increase in disorder, while a negative ΔS indicates a decrease in disorder.

Standard Entropy (S°)

Standard entropy (S°) refers to the absolute entropy of a substance at standard conditions (1 bar, 25°C). Each substance has a specific standard entropy value, which is used to calculate the change in entropy for a reaction (ΔS°rxn) by taking the difference between the total entropies of products and reactants.

Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. Understanding the stoichiometry of a reaction is essential for calculating changes in entropy, as it helps determine how many moles of each substance are involved, which directly affects the overall change in disorder during the reaction.