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Unit 2
Chemistry Definitions
Term | Definition |
---|---|
Functional group | part of the organic molecule responsible for chemical reactions |
Homologous series | series of organic compounds with the same functional group |
Structual isomer | molecules with the same molecular formula but a different structual arrangement of atoms |
Stereoisomers | compounds with the same structual formula but a different arrangement of atoms in space. |
Standard enthalpy change of combustion | when one mole of substance reacts completely with oxygen under standard conditons and with all reactants and products being in their standard states |
Standard enthalpy change of reaction | enthalpy change that takes place with the reaction being in molar quantities under standard conditions and standard states |
Standard state | physical state of a substance under standard conditions |
Heterolytic fission | breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation and an anion |
Homolytic fission | breaking of a covalent bond, with one of the bonded electrons going to each atoms |
Exothermic | refers to a reaction where the enthalpy of the products is smaller than enthalpy of the reactants resulting in heat loss to the surroundings |
Endothemrmic | refers to a reaction where the enthalpy of the products is greater than the enthalpy of the reactants resulting in heat being taken in from the surroundings |
Dynamic equilibrium | the equilibrium that exists in a closed system when the rate of the forward reaction is the same as the rate of the reverse reaction |
Le Chateliers principle | when a system in dynamic equilibrium is subjected to a change, the postion of equilibrium will shift to minimise the change |
Boltzmann distribution | distribution of energies of molecules at a particular temperature, often shown as a graph |
Average bond enthalpy | is the average enthalpy change that takes place when breaking by homolytic fission 1 mole of a given bond type in the molecules of a gaseous speacies |
Standard enthalpy change of formation | one mole of a compound is formed from its constituent elements in their standard states and under standard conditions |
Activation energy | energy required to start a reaction and used to break bonds |
Nucleophile | is an atom or a group of atoms that is attracted to an electron deficient centre or atom, where it donates a pair of electrons to form a new covalent bond |
Electrophile | an atom or group of atoms that is attracted to an electron rich centre or atom, where it accepts a pair of electrons to form a new covalent bond |
Reflux | the continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry |
Radical substitution | type of substitution reaction in which a radical replaces a different atom or group of atoms |
Radical | a species with an unpaired electron |
Mechanism | a sequence of steps showing the path taken by electrons in a reaction |
Inititation | the first step in radical subsitution in which free radicals are generated by ultraviolet radiation |
Propagation | two repeated steps in radical subsitution that build up the products in a chain reaction |
Termination | step at the end of a radical subsitution when two radical combine to form a molecule |
Aliphatic hydrocarbon | hydrocarbon with carbon atoms joined together in straight or branched chains |
Alicyclic hydrocarbons | hydrocarbon with carbon atoms joined together in a ring structure |