AQA AS CHEM 2 Key Terms Flashcards

AQA CHEM 2 Key Terms Flashcards

  • Created by: Luke
  • Created on: 15-04-13 17:59
Exothermic
Describes a reaction in which heat is given out as the reactants change to products; the temperature thus rises.
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Endothermic
Describes a reaction in which heat is taken in as the reactants change to products; the temperature thus drops
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Enthalpy Change
A measure of heat energy given out or taken in when a chemical or physical change occurs at constant pressure
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Standard Molar Enthalpy of Formation
The enthalpy change when one mole of substance is formed from its constituent elements under standard conditions, all reactants and products in their standard states.
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Standard Molar Enthalpy of Combustion
The enthalpy change when one mole of substance is completely burned in oxygen under standard conditions, all reactants and products in their standard states.
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Specific Heat Capacity
The amount of heat needed to raise the temperature of 1 gram of substance by 1 Kelvin.
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Calorimeter
An instrument for measuring the heat changes that accompany chemical reactions.
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Hess's Law
The enthalpy change for a chemical reaction is the same, whatever route is taken from reactants to products.
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Enthalpy Diagrams
Diagrams in which the enthalpies (energies) of the reactants and products of a chemical reaction are plotted on a vertical scale to show their relative levels.
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Allotropes
Pure elements which can exist in different physical forms in which their atoms are arranged differently. For example, diamond, graphite and buckminsterfullerene are allotropes of carbon.
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Thermochemical Cycle
A sequence of chemical reactions (with their enthalpy changes) that convert a reactant into a product. The total enthalpy change of the sequence of reactions will be the same as that for the conversion of the reactant to the product by any route.
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Bond Dissociation Enthalpy
The enthalpy change required to break a covalent bond with all species in the gaseous state.
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Mean Bond Enthalpy
The average value of the bond dissociation enthalpy for a given type of bond taken from a range of different compounds.
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Activation Energy
The minimum energy that a particle needs in order to react; the energy (enthalpy) difference between the reactants and the transition state
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Maxwell-Boltzmann Distribution
The distribution of energies (and therefore speeds) of the molecules in a gas or a liquid.
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Heterogeneous Catalyst
A catalyst which is in a different phase from the reactants. For example, iron (solid) in the Haber process conversion of nitrogen and hydrogen (both gases) to ammonia.
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Homogeneous Catalyst
A catalyst which is in the same phase as the reactants.
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Equilibrium Mixture
The mixture of reactants and products formed when a reversible reaction is allowed to proceed in a closed container until no further change occurs. The forward and backward reactions are still proceeding but at the same rate.
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Dynamic Equilibrium
A situation in which the composition of a mixture does not change because both forward and backward reactions are proceeding at the same rate.
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Le Châtelier's Principle
If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance.
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Chemical Feedstock
The starting materials in an industrial chemical process.
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Oxidation
A reaction in which an atom or group of atoms loses electrons.
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Oxidising Agent
A reagent that oxidises (removes electrons from) another species.
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Reduction
A reaction in which an atom or group of atoms gain electrons.
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Reducing Agent
A reagent that reduces (adds electrons to) another species.
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Redox Reaction
Short for reduction-oxidation reaction, it describes a reaction in which electrons are transferred from one species to another.
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Half Equation
An equation for a redox reaction which considers just one of the species involved and shows explicitly the electrons transferred to or from it.
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Spectator Ions
Ions that are unchanged during a chemical reaction i.e. they take no part in the reaction.
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Oxidation State
The number of electrons lost or gained by an atom in a compound compared to the uncombined atom. It forms the basis of a way of keeping track of redox (electron transfer) reactions. Also called oxidation number.
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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.
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Nucleophile
An electron pair donor
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Nucleophilic Substitution
An organic reaction in which a molecule with a partially positively charged carbon atom is attacked by a nucleophile. It results in the replacement of one of the groups or atoms on the original molecule by the nucleophile.
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Leaving Group
In an organic substitution reaction, the leaving group is an atom or group of atoms that is ejected from the starting material, normally taking with it an electron pair and forming a negative ion.
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Elimination
A reaction in which an atom or group of atoms is removed from a reactant.
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Free Radical
A chemical species with an unpaired electron - usually highly reactive.
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Electrophile
An electron-deficient atom, ion or molecule that takes part in an organic reaction by attacking areas of high electron density in another reactant.
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Electrophilic Addition
A reaction in which a carbon-carbon double bond is saturated and in which the initial reaction is an attack by an electrophile.
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Carbocation
An organic ion in which one of the carbon atoms has a positive charge.
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Positive Inductive Effect
Describes the tendency of some atoms or groups of atoms to release electrons via a covalent bond.
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Monomer
A small molecule that combines with many other monomers to form a polymer.
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Anaerobic Respiration
The process by which energy is released and new compounds formed in living things in the absence of oxygen.
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Carbon-Neutral
A process, or series of processes, in which as much carbon dioxide is absorbed from the air as is given out.
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Aldehyde
An organic compound with the general formula RCHO in which there is a C=O double bond.
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Ketone
An organic compound with the general formula R2CO (subscript 2) in which there is a C=O double bond.
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Molecular Ion
In mass spectrometry this is a molecule of the sample which has been ionised but which has not broken up during its flight through the instrument.
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Fingerprint Region
The area of an infra-red spectrum below about 1500c/m. It is caused by complex vibrations of the whole molecule and is characteristic of a particular molecule.
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Other cards in this set

Card 2

Front

Describes a reaction in which heat is taken in as the reactants change to products; the temperature thus drops

Back

Endothermic

Card 3

Front

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

Back

Preview of the back of card 3

Card 4

Front

The enthalpy change when one mole of substance is formed from its constituent elements under standard conditions, all reactants and products in their standard states.

Back

Preview of the back of card 4

Card 5

Front

The enthalpy change when one mole of substance is completely burned in oxygen under standard conditions, all reactants and products in their standard states.

Back

Preview of the back of card 5
View more cards

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madihaa

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6322

madihaa

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sorry my friend

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