Key Chemical Thermodynamics Principles Explained
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Key Chemical Thermodynamics Principles
First Law of Thermodynamics
Internal energy is equal to the heat released or absorbed by the system plus the work done by or on the system.
Standard Enthalpy of Formation
The heat change resulting from the formation of one mole of a compound from its elements in their most stable states of aggregation.
Enthalpy of a Chemical Reaction
The heat absorbed or released from the system when the reaction occurs at constant pressure.
Hess's Law
A chemical reaction can be expressed as an algebraic sum of others; its heat of reaction is equal to the algebraic sum of the heats of the partial reactions.
Bond Enthalpy (Bond Energy)
The heat flow, absolute, for the formation or rupture of a mole of bonds from the isolated atoms in their gaseous state and at constant pressure.
Entropy (DS)
A macroscopic variable that reflects the microscopic disorder of the system we are studying.
Second Law of Thermodynamics
States that in spontaneous processes, the entropy of the universe increases.
Third Law of Thermodynamics
When a substance is at 0 K as a perfect crystal, its entropy is zero.
Free Energy of Formation
The free energy change required to form a mole of a compound from its elements in their ground state under specific pressure and temperature conditions.
Chemical Kinetics and Equilibrium
Speed of a Chemical Process
The change in concentration of reactants or products with respect to time in the process.
Global Order of Reaction
The sum of partial orders for each of the reagents.
Chemical Balance (Equilibrium)
Is established when there are two opposing reactions taking place simultaneously at the same speed.
Degree of Dissociation
As one part of a chemical process, it is the ratio between the number of moles dissociated divided by the total number of initial moles.
Le Chatelier's Principle
If some of the factors that influence an equilibrium system are changed, the system evolves so that it moves in the direction that tends to counteract such change.
Precipitation Reactions
Defined as those that take place between ions in solution to form insoluble substances.
Solubility
It is the concentration in mol/L that the solute has in the solvent when the solution is saturated, measured at a given temperature.