Honors Chemistry
Study Guide – Chapter 5: Thermochemistry
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Kinetic (thermal) Energy & Potential (chemical) Energy
o Be able to define these in chemistry terms (basically what is kinetic/potential energy
and what is the most important type of kinetic/potential energy in terms of chemistry?)
Conversions between units must be memorized
o Joules, kilojoules, calories, Calories, kilocalories
First Law of Thermodynamics
o What does this law state?
o What is the significance of this law in terms of the transfer of energy between system &
surroundings?
Change in Internal Energy (ΔE) Calculations
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ΔE = q + w
Definitions of energy, heat, work, and temperature
Must know which sign (+ or –) to use for heat and work  if energy come INTO the
system it is positive, if energy LEAVES the system it is negative (see table 5.1 on pg.
174 in textbook or your notes to review this)
o What is a state function? (know some examples from this chapter of state functions)
Endothermic vs. Exothermic
o Definitions
o Sign of ΔH (+ or –)
o Enthalpy Diagrams be able to distinguish between which is an exothermic and
endothermic diagram, be able to draw enthalpy diagrams, know which is higher in
enthalpy (reactants or products) for both an endothermic and exothermic reaction
Enthalpies of Reaction
o Thermochemical Equations
 2 ways to write a thermochemical equations  heat is either added as a
reactant or product OR ΔH at the end is either positive or negative
 Be able to recognize (and write) if a reaction is exo or endothermic based on its
thermochemical equation
o Thermochemical Equations & Stoichiometry
 Be able to calculate the enthalpy change (ΔH) associated with a particular
mass of any reactant or product when given a thermochemical equation (or
vice-versa, be able to find mass when given a particular enthalpy change)
Calorimetry
o What 2 factors affect the temperature change of a substance being heated?
o Definitions of Heat capacity & specific heat
o Calculations using q = mCpΔT
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 Must memorize the specific heat of water only (4.184 J/g°C or 1 cal/g°C)
How does the process of calorimetry work? (what is the basic principle behind it?)
Be able to solve calorimetry problems for any variable (remember… –qlost = + qgained)
Hess’s Law
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Be able to determine the enthalpy of a chosen reaction (ΔH) given several
thermochemical equations to rearrange according to Hess’s Law
o Remember, whatever is done to the reaction must also be done to the associated ΔH
o Recall that this law is possible because enthalpy is a state function
Enthalpies of Formation
o Definition of enthalpy of formation (ΔHf°)
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What is the most stable form of an element? What is the ΔHf° of an element in its most
stable form?
Be able to write standard enthalpy of formation equations  always form ONE MOLE
of the compound from its standard state elements and look up ΔHf° in Appendix C
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Be able to use Appendix C (and/or given ΔHf°) values appropriately
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Be able to calculate ΔHrxn° values (or ΔHf°) using the equation:
ΔHrxn° = Σ[ΔHf°(products)] – Σ [ΔHf(°reactants)]