AP Chemistry Flashcards: Absolute Entropy and Entropy Change
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
What fundamental data is required to calculate the standard entropy change for a process?
To calculate the standard entropy change, you need the absolute entropies (or standard molar entropies) of all the reactant and product species involved in the process.
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What fundamental data is required to calculate the standard entropy change for a process?
To calculate the standard entropy change, you need the absolute entropies (or standard molar entropies) of all the reactant and product species involved in the process.
A reaction has a negative ΔS°reaction. What does this imply about the entropies of the species involved?
This implies that the sum of the absolute entropies of the reactants is greater than the sum of the absolute entropies of the products, resulting in a net decrease in entropy.
What is another term for 'absolute entropies' used in calculating entropy change?
Absolute entropies are also commonly referred to as standard molar entropies, symbolized as S°.
What is the primary purpose of calculating the standard entropy change for a chemical process?
The primary purpose is to quantify the change in disorder or randomness for a reaction when all substances are in their standard states.
How is the standard entropy change for a reaction determined?
It is determined by finding the difference between the sum of the absolute entropies of the products and the sum of the absolute entropies of the reactants.
What is the formula to calculate the standard entropy change for a reaction?
The standard entropy change is calculated using the formula: ΔS°reaction = ΣS°products − ΣS°reactants.
What is the standard entropy change (ΔS°reaction)?
It is the change in entropy for a chemical or physical process, calculated from the absolute entropies of the species involved when they are in their standard states.
In the entropy change formula, what does 'ΣS°reactants' represent?
It represents the sum of the standard molar entropies of all the reactants, each multiplied by its stoichiometric coefficient from the balanced chemical equation.
In the entropy change formula, what does 'ΣS°products' represent?
It represents the sum of the standard molar entropies of all the products, each multiplied by its stoichiometric coefficient from the balanced chemical equation.
If the sum of the absolute entropies of the products is greater than that of the reactants, what will be the sign of ΔS°reaction?
The sign of ΔS°reaction will be positive, indicating an overall increase in entropy for the reaction.