Download 17.2 section summary

SECTION SUMMARY
17.2 Measuring and Expressing Enthalpy Changes Summary:
A calorimeter is a device used to measure the absorption or release of heat in
chemical and physical processes. In calorimetry, the heat released by the system is
equal to the heat absorbed by its surroundings. Conversely, the heat absorbed by a
system is equal to the heat released by its surroundings. For systems at constant
pressure, the heat changes that occur are the same as changes in enthalpy, symbolized
as H. T measure the enthalpy change for a reaction in aqueous solution, it is
necessary to measure the initial or final temperature of the system and the mass of the
water in the system.
It is true that the sign of H is negative for an exothermic reaction. In endothermic
reactions, the potential energy of the products is higher than the potential energy of
the reactants.
17.2 Measuring and Expressing Enthalpy Changes Vocabulary Terms:
calorimetry:
the precise measurement of heat flow out of a
system for chemical and physical processes
calorimeter:
an insulated device used to measure the absorption
or release of heat in chemical or physical processes
enthalpy, (H):
the heat content of a system at constant pressure
thermochemical equation:
a chemical equation that includes the enthalpy
change
heat of reaction:
the enthalpy change for a chemical equation exactly
as it is written
heat of combustion:
the heat of reaction for the complete burning of one
mole of a substance
2NaHCO3(s) → Na2CO3(s) + H2O(g) + CO2(g) ΔH = 129 kJ
CaO(s) + H2O(l) → Ca(OH)2(s)
ΔH = −65.2 kJ
The End of the Summary
an example of heat of combustion
an example of exothermic process