Final answer:
The standard entropy change (Δ∘rxn) for the reaction C2H2(g) → C6H6(l) at 25.0 ∘C is calculated to be 68.8 J/(mol•K).
Step-by-step explanation:
To calculate the standard entropy, Δ∘rxn, we need to find the difference in entropy between the products and reactants. The standard entropy change for the reaction C2H2(g) → C6H6(l) can be calculated using the standard entropy values given in Appendix G. The standard entropy of C2H2(g) is 200.9 J/(mol•K), and the standard entropy of C6H6(l) is 269.7 J/(mol•K). Therefore, the standard entropy change (Δ∘rxn) is the difference between these two values:
Δ∘rxn = S°(C6H6(l)) - S°(C2H2(g)) = 269.7 J/(mol•K) - 200.9 J/(mol•K) = 68.8 J/(mol•K).