Chemistry
Chemistry 18: 4-5
Homework
Measuring Entropy
Chapter 18: 4-5 Homework
- Reading Preparation
- WebLecture
- Study Activity
- Preparation work for chat
- Online Quiz
- Lab Instructions
Reading Preparation
Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 13: Sections 4 to 5.
Study Notes
- 18.4 Entropy increases with temperature and with changes of state involving the input of heat (from solid to liquid, from liquid to gas). The more ways a molecule can change position or move, the greater the number of microstates it can have and the higher its entropy level.
- 18.5 Entropy, like enthalpy and potential energy, is a state value: we measure the difference between two states, but do not measure the absolute zero value of entropy except to establish a baseline under specific conditions. Reactions will be
- spontaneous if they are both exothermic and entropy increases
- spontaneous if they are exothermic and the decrease in entropy is small enough
- spontaneous if they are endothermic and the increase in entropy is big enough
- never spontaneous if they are endothermic and entropy decreases
Key Formula
| Principle | Formula | Notes |
|---|---|---|
| Change in Entropy of Reaction System |
ΔrS°: Entropy change for reaction at STP
ΣnS°: Sum of entropy at STP P and R : Products and Reactants |
|
| Change in Universe |
ΔS°: Entropy change for universe at STP
ΔS°: Change in entropy at STP S and E : System and Environment (surroundings) |
| Reaction Type | ΔH°(system) | ΔS°(system | Spontaneous 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.
- Under "THERMODYNAMICS"
- Entropy
- Entropy and Temperature
- Using Free Energy
- Enthalpy and Entropy Contributions to K
- Entropy
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
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
Chapter Quiz
- There is no chapter quiz YET.
(Aligns to) AP #15 GUIDED INQUIRY — Titration Methods — Phase II
Carry out your acid-base titration and analyze your data.
Resources:
- AP2009 #6 Standardization of of solution using primary standards
- APGIE Investigation 14 Acid-Base Titration: How Do the Structure and the Initial Concentration of an Acid and a Base Influence the pH of the Result Solution During a Titration?
- IGHCE Lab 11.4 Standardize a Hydrochloric Acid Solution by Titration
- There is no alternate form for this lab
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