AS Chemistry Unit 2 - Important terms

help to revise key terms that the examiners may ask you to define.

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Important Terms

Activation Energy - The minimum energy the particle needs in order to react.

Alkane - A hydrocarbon with single bonds only and with a general formula of Cn H2n+2.

Catalyst - A substance that alters the rate of a chemical reaction but is not used up in the reaction.

Heterogenous Catalyst - A catalyst with a different phase to the reactants

Carbon Neutral - A process in which as much carbon dioxide is taken in from the air as is given out.

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Important Terms

Disproportionation - Describes a redox reaction in which the oxidation number of some atoms of a particular element increases and that of other atoms of the same element decreases.

Dynamic Equlibrium - A situation in which the composition of a reaction mixture does not change because both the forward and the backward reaction are occuring at the same rate.

Electrophile - Electron pair acceptor.

Elimination - A reaction in which an atom or group of atoms is removed from a reactant.

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Important Terms

Endothermic - Describes a reaction in which heat is taken in as the reactants change to the products, the temperature drops.

Enthalphy Change - A measure of heat energy given out or taken in when a chemical or physical change occurs at a constant pressure.

Equlibrium Mixture - The mixture of reactants and products formed when a reversible reaction is allowed to proceed in a closed container until no futher changes occur.

Exothermic - Describes a reaction in which heat is given out as the reactants change to products, the temperature rises.

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Important Terms

Fingerprint Region - The area of an infared spectrum bellow 1500cm-1. It is caused by complex vibrations of the whole molecule, it is unique toeach molecule.

Isomer - Compounds with the same molecuar formula but a different structual formula.

Leaving Group - An atom or group of atoms that is ejected in an organic substitution reaction.

Maxwell-Boltzmann Distribution - The distribution of energies of the molecules in a gas or liquid.

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Important Terms

Mean Bond Enthalphy - The average value of bond dissociation enthalphy for a given typeof bond taken from a range of different compounds.

Nucleophile - An electron pair donor.

Oxidation - A reaction in which an atom or group of atoms looses electrons.

Oxidation State - The number of electrons lost or gained by an atom in a compound compared to that of an uncombined atom.

Oxidising agent - A reagent that oxidises another species, removes electrons from.

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Important Terms

Reducing Agent - A reagent that reduces another species, adds electrons to.

Reduction - A reaction in which an atom or group of atoms gain electrons.

Specific Heat Capacity - The amount of heat needed to raise the temperature of 1g of a substance by 1K.

Standard Molar Enthalpy Change Of Combustion - The amount of heat energy given out when 1 mole of a substance is completley burned in oxygen with all reactants and products in their standard state.

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Important Terms

Standard Molar Enthalpy Change Of Formation - The heat change when 1mole of substance is formed from its elements with all reactants and products in their standard states.

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