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Chemistry 18: 4-5

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Measuring Entropy

Chapter 18: 4-5 Homework

Reading Preparation

Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 13: Sections 4 to 5.

Study Notes

Key Formula

Change in Entropy of Reaction System Δ r S o   =   Σ n   S o ( P )   Σ n   S o ( R )   Δr: Entropy change for reaction at STP
ΣnS°: Sum of entropy at STP
P and R : Products and Reactants
Change in Universe Δ   S o   =   Δ   S o ( S )   +   Δ   S o ( E )   ΔS°: Entropy change for universe at STP
ΔS°: Change in entropy at STP
S and E : System and Environment (surroundings)
Reaction TypeΔH°(system)ΔS°(systemSpontaneous at STP?
1 Exothermic, < 0 Positive, > 0 Spontaneous at all T
ΔS°(universe) > 0
2 Exothermic, < 0 Negative, < 0 Spontaneous at low temperatures; depends on ΔH and ΔS
3 Endothermic, > 0 Positive, > 0 Spontaneous at high temperatures; depends on ΔH and ΔS
4 Endothermic, > 0 Negative, < 0 Not Spontaneous at any temperature

Read the following weblecture before chat: Measuring Entropy

Study Activity

Videos for Chapter 18: Principles of Chemical Reactivity: Entropy and Free Energy

Review the Videos at Thinkwell Video Lessons.

    • Entropy
      • Entropy and Temperature
    • Using Free Energy
      • Enthalpy and Entropy Contributions to K

Use the instructions at Investigating Entropy in Chemical Reactions from SciencebySimulation and the linked ChemReaX simulator to conduct the exothermic virtual reaction. How does changing temperature affect free energy changes? How does changing temperature affect entropy changes?

Chat Preparation Activities

Chapter Quiz

(Aligns to) AP #15 GUIDED INQUIRY — Titration Methods — Phase II

Carry out your acid-base titration and analyze your data.