OCR Chemistry Definitions Unit 2

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  • Created by: Beth
  • Created on: 01-06-13 22:05
Empirical formula
The simplest whole number ratio of atoms of each element 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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Structural formula
The minimal detail that shows the arrangement of atoms in a molecule
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Displayed formula
The simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving a carbon skeleton and functional groups
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Homologous series
A series of organic compounds having the same functional group and the same general formula.
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Functional group
A group responsible for the characteristic reactions of a compound
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Structural isomers
Compounds with the same molecular formula but a 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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E/Z isomerism
A type of stereoisomerism, where the C=C bond can’t rotate and it has 2 different groups attached to each carbon
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Cis-trans isomerism
A type of E/Z isomerism which has 2 of the same groups on each of the carbon atoms in a C=C bond
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Homolytic fission
The breaking of a covalent bond forming two radicals
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Heterolytic fission
The breaking of a covalent bond forming a cation and an anion
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Radical
A species with an unpaired electron
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Curly arrows
Show the movement of an electron pair in either the breaking or the formation of a covalent bond
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Nucleophile
An electron pair donor
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Electrophile
An electron pair acceptor
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Atom economy
Molecular mass of the desired products X sum of molecular masses of all products
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Hydrocarbon
A compound containing carbon and hydrogen only
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Standard conditions
Pressure of 100 KPa and temperature of 298K and a concentration of 1.0mol dm^-3, in solution
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Standard enthalpy change of reaction
The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions
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Enthalpy change of formation
The enthalpy change that takes place 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
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions and all products being in their standard states
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Exothermic reaction
A reaction in which the enthalpy of the reactants is greater than the enthalpy of the products, releasing heat into the surroundings
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Endothermic reaction
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken from the surroundings
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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’s law
If a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change for each route is the same
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Le Chatelier’s principle
When a system in dynamic equilibrium is subjected to a change, the position of 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

The minimal detail that shows the arrangement of atoms in a molecule

Back

Preview of the back of card 4

Card 5

Front

The simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving a carbon skeleton and functional groups

Back

Preview of the back of card 5
View more cards

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