Chem 5 Definitions

definitions that are really hard to remember

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  • Created by: Ella Shaw
  • Created on: 17-06-12 08:30

Enthalpy change

A heat change during a physical or chemical change at constant pressure

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Standard enthalpy change

the enthalpy change per mole at a specified temperature (usually 298K) and a pressure of 100kPa with all substances being in their standard states

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Standard State

The standard state of a substance at a given temperature is its pure most stable form at 100kPa

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Standrad enthalpy of atomisation

the enthalpy change that accompanies the formation of one mole of gaseous atoms from the element in its standard state under standard conditions

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First ionisation energy

the standard enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single positive charge

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Second ionisation energy

refers to the loss of a mole of electrons from a mole of singly positively charged ions

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First electron affinity

The standard enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single neagtive charge

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Second electron affinity

the ethalpy change when one mole of electrons is added to a mole of gaseous ions each with a single negative charge to form ions each with two negative charges 

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Lattice formation enthalpy

the enthalpy change when one mole of a solid ionic compound is formed from its gaseous ions

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Enthalpy of lattice dissociation

the enthalpy change when one mole of an ionic compound separates into its gaseous ions

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Enthalpy of hydration

the standard enthalpy change when water molecues surround one mole of gaseous ions

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Enthalpy of solution

the standard enthalpy change when one mole of a solute dissolved completely in sufficient solvent to form a solution in which the molecules or ions are far enough apart not to interact with each other

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Bond dissociation enthalpy

the enthalpy change that accompanies the breaking of a covalent bond in a gaseous molecule to form two gaseous free radicals, averaged over a range of compounds

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The mean bond enthalpy

the average of several values of the bond dissociation enthalpy for a given type of bond, taken from a range of different compounds

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A spontaneous or feasible reaction

one that has natural tendency to occur without being driven by external influences

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The transition metals

elements that have an incomplete d- (or f-) sub energy level either in the element or one of its ions

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A ligand

An atom, ion or molecule that can form one or more co-ordinate bond with a metal ion by donating one or more lone pair of electrons

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A catalyst

a substance that speeds up a chemical reaction without itself being change at the end of the reaction. it does this by providing an alternative reaction pathway with a lower activation energy

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Lewis Acid/Base

Lewis Acid- An electron pair acceptor

Lewis Base- An electron pair donor

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