Question

Use data from Appendix IIB in the textbook to calculate ΔS°rxn for each of the following reactions.

a. C₂H₄(g) + H₂(g) → C₂H₆(g)
b. C(s) + H₂O(g) → CO(g) + H₂(g)
c. CO(g) + H₂O(g) → H₂(g) + CO₂(g)
d. CO(g) + 2H₂(g) → CH₃OH(g)

Answer 1

To calculate the standard entropy change for a chemical reaction, you subtract the sum of the standard molar entropies of the reactants from the sum of the standard molar entropies of the products, based on data from a source like Appendix G.

Step-by-step explanation:

To calculate the standard entropy change (ΔS°rxn) for a chemical reaction, one must consider the standard molar entropies of the reactants and products listed in thermodynamic tables, such as Appendix G referenced here. The ΔS°rxn is found by subtracting the sum of the standard molar entropies of the reactants from the sum of the standard molar entropies of the products, each multiplied by their respective stoichiometric coefficients in the balanced equation.

For a generic chemical reaction, such as:

A(g) + B(g) → C(g) + D(g)

The standard entropy change would be calculated as:

ΔS°rxn = [Σ(°Sproducts) - Σ(°Sreactants)]

Here it would be:

ΔS°rxn = [(S°C + S°D) - (S°A + S°B)]

Please note that without specific data from Appendix G, the actual values cannot be calculated in this example.