Definitions Unit 5 Chemistry

Thermodynamics and further physical and inorganic Chemistry.

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  • Created by: HASNAAN
  • Created on: 22-05-09 19:39

Enthalpy Change

The heat energy taken in or given out during any change. Under constant pressure.



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Enthalpy of Formation

The enthalpy change when one mole of a compound is formed from its elements under standard conditions. All reactants and prducts in their standard states.

Standard conditions :- Pressure = 100 Kpa, Temprature = 298 K


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Bond Dissociation Energy

The standard molar enthalpy change which accompanies the breaking of a covalent bond in gaseous molecule to form two free radicals also in the gas phase.

Cl2 ----> 2Cl.


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Enthalpy of ionisation

Standard molar enthalpy change for the removal of an e- from a species in the gas phase to form a +ve ion and an e-.

e.g. Na (g) -------> Na+ (g) + e- (g)

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Enthalpy of Atomisaion.

The standard enthalpy change which accompanies the formation of one mole of gaseous atoms.

1/2Cl (g) -----> Cl (g)

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Electron Affinity

The standard molar enthalpy change when an e- is added to an isolated atom in the gas phase.

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Enthalpy of solution

Standard enthalpy change for the process in which one mole of an ionic solid dissolves in an amount of water large enough to ensure dissolved ions are well seperated and do not interact with one another.

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Lattice Enthalpy

(Diss) the standard enthalpy change which accompanies the seperation of one mole of a solid ion lattice into it's gasseous ions.

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