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Chapter 6 Study Guide
Chapter 6 is about thermochemistry, which is an
outgrowth of the subject thermodynamics, which,
as the name suggests is the study of the motion of heat and work.
In thermodynamics and thermochemistry the terms "heat" and
"work" are given very specific meanings, and several other
quantities are introduced, namely internal energy
and enthalpy. (The rest of the subject
of thermodynamics is introduced in Chapter 17). The
first part of Chapter 6 presents the "style" of the
subject and formal statement of the First Law of Thermodynamics,
and the definition of enthalpy. Enthalpy is shown to
be very applicable to chemical reactions done at
constant pressure (most of them), and calorimetry, the
art of measuring enthalpy and energy changes, is discussed
at length. Finally, Hess's Law of Heat Summation and
the idea of enthalpy of formation of a compound are
introduced and their utility is explained.
Suggested Problems
The following problems (in the textbook) are illustrative of the
important concepts covered in this chapter, and are of comparable
(or greater!) difficulty with what you might see on homeworks or exams:
Chapter 6, problems 28,29,30, 31, 32, 34, 35, 37, 40, 43, 46, 54, 55,
59, 63, 65, 69, 71-75, 77, 78, 82, 84.
You should be able to:
- Write and manipulate the first law of thermodynamics, and the
definition of enthalpy
- Define and explain heat and work.
- Use reaction enthalpies
- Use specific heats and heat capacities in calorimetry problems
- Apply Hess's Law
- Write "formation" reaction equations
- Use "heat of formation" data to calculate reaction enthalpies.
Important topics and Concepts
- The formal language and definitions of thermodynamics
- Energy
- Heat
- Work
- Enthalpy
- Systems
- Surroundings
- State Functions
- Exothermic and endothermic
- Pressure-volume work
- The First Law of Thermodynamics
- Conservation of Energy
- Heat of Reaction
- Why enthalpy is more useful than internal energy
- Stoichiometry
- Calorimetry
- (Molar) Heat Capacity
- Specific Heat
- How a calorimeter works
- Hess's Law
- You can add heats of reaction for
a process involving several steps!
- Enthalpy of Formation under standard conditions
- How they're useful - can calculate heats of reaction!
- Ionic systems - they work a little differently here...
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