AS Chemistry Unit 2

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Empirical Formula
The simplest whole number ratio of atoms of each element present in a compound
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Molecular Formula
The actual number of atoms of each element in a molecule
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General Formula
The simplest algebraic formula of a member of a homologous series
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Homologous series
Series of organic compounds having the same functional group but with each successive member differing by CH2
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Structural isomers
Compounds with the same molecular formula but different structural formula
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Stereoisomers
Compounds with the same structural formula but with a different arrangement in space
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Homolytic Fission
The breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals
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Heterolytic Fisssion
The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation and an anion
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Radical
A species with an unpaired electron
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Nucleophile
An electron pair donor
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Electrophile
An electron pair acceptor
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Addition reaction
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
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Substitution reaction
A reaction in which an atom or group of atoms is replaced by a different atom or group of atoms
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Elimination reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule
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Atom Economy
molecular mass of desired products/molecular mass of all products x 100
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Percentage yield
actual mass of desired product/max possible mass of desired product x 100
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Hydrocarbon
A compound of hydrogen and carbon only
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Sigma bond (σ bond)
Bond formed directly between two atoms by the head on overlap of orbitals
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Pi bond (π bond)
Bond formed above and below the plane of an atom by the sideways overlap of p-orbitals
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Polymer
Long chain molecule built up from monomer units
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Monomer
Small molecule that combines with many other monomers to form a polymer
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Activation energy
The minimum energy required to start a reaction by breaking bonds
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Standard conditions
100kPa (1 atm), 298K and a concentration of 1moldm-3
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Enthalpy, H
The heat content that is stored in a chemical system
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Exothermic ΔH = - ve
Reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants
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Endothermic ΔH = + ve
Reaction in which the enthalpy of the products is greater than the enthalpy of the reactants
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Standard Enthalpy change of reaction ΔHrΘ
The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states
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Enthalpy change of formation ΔHfΘ
The enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions
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Enthalpy change of combustion ΔHcΘ
The enthalpy change when one mole of a substance reacts completely with oxygen under standard conditions, all reactants and products being in their standard states
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Average bond enthalpy
The average enthalpy change that takes place when breaking by homolytic fission 1 mole of a given type of bond in the molecules of a gaseous species
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Hess' Law
If a reaction can take place by more than one route, the total enthalpy change is independent of the route taken
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Specific heat capacity
The energy required to raise the temperature of 1g of a substance by 10C
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Catalyst
Increases the rate of a reaction without being consumed by the overall reaction
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Heterogeneous catalysis
The catalyst is in a different physical state to the reactants
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Homogeneous catalysis
The catalyst is in the same physical state as the reactants
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Dynamic equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction
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le Chatelier’s principle
When a system in dynamic equilibrium is subjected to a change, the position of the equilibrium will shift to minimise the change
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Other cards in this set

Card 2

Front

The actual number of atoms of each element in a molecule

Back

Molecular Formula

Card 3

Front

The simplest algebraic formula of a member of a homologous series

Back

Preview of the back of card 3

Card 4

Front

Series of organic compounds having the same functional group but with each successive member differing by CH2

Back

Preview of the back of card 4

Card 5

Front

Compounds with the same molecular formula but different structural formula

Back

Preview of the back of card 5
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