Consider the following reaction: What is Δ_rS° for the above reaction in J/mol K? A)-49.9 J/mol K B)49.9 J/mol K C)80.7 J/mol K D)115.2 J/mol K E)-80.7 J/mol K

Question

Quizplus · Accepted Answer

The standard entropy change can be calculated using the following formula: ΔS° = ΣS°(products) - ΣS°(reactants). 
From the balanced chemical equation, we can see that there are 1 mole of gas (CO2) on the product side and 2 moles of gas (CO and O2) on the reactant side. 
Using the standard molar entropy values from a data table: 
ΔS° = [S°(CO2)] - [S°(CO) + S°(O2)] 
ΔS° = [(213.7 J/mol K)] - [(197.9 J/mol K) + (205.0 J/mol K)] 
ΔS° = -80.7 J/mol K (negative sign indicates a decrease in entropy) 
Therefore, the answer is E.

Consider the Following Reaction