Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
Calculate the temperature in kelvins above which this reaction is spontaneous.
![<Hw8-Chapter19
+ Gibbs Free Energy: Equilibrium Constant
10 of 17 :
I Review | Constants | Periodic Table
Calcium oxide, CaO, is manufactured by decomposition
of calcium carbonate, CaCO3. in a furnace at 500 K:
Relation among thermodynamic quantities
CaCO, (s)->CaO(s) + CO2(g)
The thermodynamic properties for a reaction are related by the equation that defines the standard free energy. AG", in kJ/mol:
The spontaneity of a reaction can be determined from
the free energy change for the reaction, AG
AG"
ΔΗ'
TAS
• A reaction is spontaneous when the free
energy change is less than zero.
• A reaction is nonspontaneous when the
free energy change is greater than zero.
• A reaction is in equilibrium when the free
energy change is equal to zero.
where AH® is the standard enthalpy change in kJ/mol and AS° is the standard entropy change in J/(mol - K). A good
approximation of the free energy change at other temperatures, AGT. can also be obtained by utilizing this equation and assuming
enthalpy (AH°) and entropy (AS®) change little with temperature.
Part A
For the decomposition of calcium carbonate, consider the following thermodynamic data (Due to variations in thermodynamic values
for different sources, be sure to use the given values in calculating your answer.):
| ΔΗ
178.5kJ/mol
ASan 161.0J/(mol - K)
Calculate the temperature in kelvins above which this reaction is spontaneous.
Express your answer to four significant figures and include the appropriate units.
> View Available Hint(s)
HA
T =
Value
Units
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