Organic Chemistry Definitions OCR Unit 2 4.5 / 5 based on 3 ratings ? ChemistryFunctional GroupsEnthalpyEquilibriaIntermolecular forcesBonding & shapesASOCR Created by: FrankieOCreated on: 30-04-15 18:08 Hydrocarbon A compound of hydrogen and carbon only 1 of 27 Empirical formula The simplest whole number ratio of atoms of each element present in a compound 2 of 27 Molecular formula The actual number of atoms of each element in a molecule 3 of 27 General formula The simplest algebraic formula of a member of a homologous series 4 of 27 Homologous series Series of organic compounds having the same functional group but with each successive member differing by CH₂ 5 of 27 Structural isomers Compounds with the same molecular formula but different structural formula 6 of 27 Stereoisomers Compounds with the same structural formula but with a different spatial arrangement 7 of 27 Homolytic fission The breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals 8 of 27 Heterolytic fission The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation and an anion 9 of 27 Radical A species with an unpaired electron 10 of 27 Electrophile An electron pair acceptor 11 of 27 Nucleophile An electron pair donor 12 of 27 Atom economy calculation (Molecular mass of desired products/ Molecular mass of all products) x 100 13 of 27 Percentage yield calculation (Actual mass of desired product/ Max possible mass of desired product) x 100 14 of 27 Sigma bond (σ bond) Bond formed directly between two atoms by the head on overlap of orbitals 15 of 27 Pi bond (π bond) Bond formed above and below the plane of an atom by the sideways overlap of p-orbitals 16 of 27 Activation energy Minimum energy with which particles must collide in order to react 17 of 27 Standard conditions 100kPa (1 atm), 298K (25*C) and a concentration of 1 mol dm^-3 18 of 27 Enthalpy, H The heat content (energy) that is stored in a chemical bonds 19 of 27 Exothermic ΔH = - ve Reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants 20 of 27 Endothermic ΔH = + ve Reaction in which the enthalpy of the products is greater than the enthalpy of the reactants 21 of 27 (Standard) enthalpy change of combustion ΔHcΘ Energy transferred when one mole of an element or compound reacts completely with oxygen (under standard conditions) 22 of 27 (Standard) enthalpy change of formation ΔHfΘ Energy transferred when one mole of a compound is formed from its elements (under standard conditions) 23 of 27 Hess' law The enthalpy change of any reaction is independent of the route taken 24 of 27 Catalyst Increases the rate of a reaction without being consumed by the overall reaction (lowers the activation energy needed) 25 of 27 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 26 of 27 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 27 of 27
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