1. Heat of Reaction Heat of Solution Heats of Fusion and Vaporization
Chapter 16 Notes, part III
Heat of Reaction
Heat of Solution
Heats of Fusion and Vaporization

2. Heat in Reactions
Enthalpy (H)—the internal heat content of a substance.
At constant pressure, the change in enthalpy (DH) is the same as heat lost/gained.
DH=mCpDT

3. Heat of Reaction
A thermochemical equation is an equation that includes the heat change (DH) that occurs during that reaction.
The heat of reaction is the heat change for the equation as written.
NOTE: There is absolutely no reason for this animation.

4. Heat of Reaction
In a reaction, if DH is negative the reaction is exothermic.
If DH is positive, the reaction is endothermic.
Why?

5. Using Heat of Reaction
Heat of reaction gets used the same way as calculating stoichiometry.

6. Heat of Solution
Heat that is produced or absorbed by the dissolving of a substance into water.

7. Heat and State Changes
It takes energy for a substance to change phases.
The amount of heat absorbed by one mole of a substance going from solid to liquid is the molar heat of fusion (DHfus).
The amount of heat absorbed by one mole of a substance going from liquid to gas is the molar heat of vaporization (DHvap).

8. Practice Problem #1
How much heat does it take to raise the temperature of 1.3g of ice at oC to water at 76.0oC?
Cice=2.1J/goC
DHfus=6.01 kJ/mol
DHvap=40.7 kJ/mol

9. Practice Problem #2
How much heat does it take to change 22.7g of solid ethanol from oC (its freezing point) to ethanol vapor at 78.5oC (its boiling point)?
DHfus=4.60 kJ/mol
DHvap=43.5 kJ/mol

10. Practice Problem #3
How much required to heat a 3.55g block of ice at -62oC to water vapor at 115oC?
DHfus=6.01 kJ/mol
DHvap=40.7 kJ/mol
Csteam=1.7 J/goC
Cice=2.1J/goC