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Module 5 Chapter 22 (22.4 Entropy (Predicting (Solid→ Liquid→ Gas more…
Module 5 Chapter 22
22.1 Lattice Enthalpy
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Lattice Enthalpy- Enthalpy change associated with the formation of one mole of an ionic compound from its gaseous ions under standard conditions (ΔLE H)
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Key enthalpy changes
Standard enthalpy change of formation- enthalpy change associated with the formation of 1 mole of a compound from its elements under standard conditions, with reactants and products i standard states (ΔfH⦵)
Standard enthalpy change of atomisation- enthalpy change associated with the formation of 1 mole of gaseous atoms from the element in its standard state under standard conditions (Δat H⦵)- endo
First ionisation energy- enthalpy change required to remove one electron from each atom in 1 mole of gaseous atom to form 1 mole of gaseous 1+ ions (ΔIE H⦵)- endo
First Electron Affinity- enthalpy change when 1 electron is added to each atom in 1 mole of gaseous atoms to form 1 mole gaseous 1- ions (ΔEA H)- first is exo but second is endo
Second electron affinity endothermic because electron gained by negative ion so repels- energy must be put in to force negatively charge electron on ion
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22.4 Entropy
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Entropy (ΔS)- measure of dispersal of energy within the chemicals making up the system, measure of disorder
Predicting
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In equation whichever side has more gaseous molecules has higher entropy (more spread of and more random) , if products ΔS positive, if reactants ΔS negative
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