IB HL Chemistry Definitions - Energetics

Terms in this set (19)

Enthalpy
the total energy of a system, some of which is stored as a chemical potential energy in the chemical bonds
Enthalpy Change
The change in the potential energy of the bonds
Endothermic Reaction
total enthalpy of the products is greater than the total enthalpy of the reactants. Then heat energy in absorbed from the surroundings and gets cooler
Exothermic Reaction
the total enthalpy of the products is lower than the total enthalpy of the reactants. Then the heat energy is lost to the surroundings and gets hotter
Thermochemical Standard Conditions
298K and 101.3kPa
Law of Conservation of Energy
states that energy cannot be created nor destroyed
Hess's Law
total enthalpy change on converting a given set of reactants to a particular set of products is constant
Bond Enthalpy
average value of a dissociation of a particular type of bond measured over a range of molecules. Endothermic reaction
Bond Dissociation Energy
the enthalpy change when one mole of a bond is broken
Standard Enthalpy Change of Formation
the amount of energy evolved or absorbed in the formation of one mole of the compound, in its standard state, from its elements in their standard state
Standard Enthalpy Change of Combustion
the enthalpy change when one mole of the compound undergoes complete combustion in excess oxygen under standard conditions. Exothermic Reaction
Standard Enthalpy Change of Atomisation
the enthalpy change required to produce one mole of gaseous atoms of an element from the element in the standard state
Electron Affinity
the enthalpy change when one mole of gaseous atoms or anions gains electrons to form a mole of negatively charged ions
Lattice Enthalpy
the energy required to convert one mole of the solid compound into gaseous ions. Endothermic
Magnitude Depends Upon: Greater Charge, Size
Ionization Energy
the enthalpy change for one mole of a gaseous element or cation to lose electrons to form a mole of a positively charged gaseous ions
Born-Haber Equation
Enthalpies of atomisation+ Electron affinity + Ionisation Energy = Enthalpy of formation + Lattice Enthalpy
Enthalpy Change of Solution
Enthalpy change when one mole the substance is dissolved in water to form dilute aqueous solution
Enthalpy Change of Hydration
when one mole of the gaseous ion is added to excess water to form dilute solution. Exothermic
Enthalpy of Solution Equation
Lattice enthalpy + Sum of hydration enthalpies
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