Chemistry Unit 2 Key Definitions

Providing definitions for all the words that are likely to be asked in the exam.

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Activation energy

An activation energy is the MINIMUM energy required for a particle to react.

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A catalyst is a substance that alters the rate of a reaction BUT IS NOT USED UP in the reaction

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Dynamic Equilibrium

Dynamic equilibrium is a situation in which the FORWARD AND BACKWARD REACTIONS ARE OCURRING AT THE SAME RATE.

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Electrophillic addition

Electrophillic addition occurs when an ALKENE is attacked by an electrophile eg. HBr

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Elimination occurs when an OH ion is reacted with a HALOALKANE in a HOT ETHANOLIC mixture

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Enthalpy Change

Enthalpy change is a measure of HEAT ENERGY given out or took in at CONSTANT PRESSURE

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Enthalpy diagrams

Enthalpy diagrams plot ENERGY LEVELS of REACTANTS and PRODUCTS on a vertical scale

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Fingerprint Region

The fingerprint region is the area of an INFRA-RED SPECTRUM below 1500CM that is INDIVIDUAL TO EACH MOLECULE.

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Maxwell-boltzmann distribution

The Maxwell-boltzmann distribution shows the distribution of ENERGIES/SPEEDS of molecules in GAS/LIQUID

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Mean Bond Enthalpy

Mean Bond Enthalpy is the AVERAGE ENTHALPY required to break a particular bond.

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Molecular Ion

Molecular ion in MASS SPECTROMETRY is a molecule that had been IONISED but not BROKEN during spectrometry.

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Nucleophillic Substitution

Nucleophillic Substitution occurs when an OH ion is reacted in a COLD AQUEOUS solution.  

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Oxidation state

The oxidation state is the NUMBER of ELECTRONS LOST compared to uncombined ATOM (0).

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Standard enthalpy of combustion

Standard enthalpy of combustion is the enthalpy change when 1 MOLE of a substance is completely BURNED IN OXYGEN under STANDARD STATES AND CONDITIONS.

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Standard enthalpy of formation

Standard enthalpy of formation is the enthalpy change when 1 MOLE of a substance is formed from its ELEMENTS under STANDARD STATES AND CONDITIONS.

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