Unit 2 Flashcards
Enthalpy (H)
The heat content of a system at constant pressure
Enthalpy Change (^H)
The heat added to a system at a constant pressure
Standard Enthalpy Change of Formation (^fH)
The enthalpy change when one mole of a substance is formed from its constituent elements in their standard states under standard conditions
Standard Enthalpy Change of Combustion (^cH)
Enthalpy change when one mole of a substance is completely combusted in oxygen under standard conditions
Hess’s Law
States that the total Enthalpy change for a reaction is independent of the route taken from the reactant to the product
Bond Enthalpy
Is the enthalpy required to break a covalent X-Y bond into X atoms and Y atoms, all in the gas phase
Average Bond Enthalpy
Average value of the enthalpy required to break a given type of covalent bond in the molecules of gaseous species
The Rate of Reaction
Is the change in concentration of a reactant or product per unit time
Activation Energy
Is the minimum energy required to start a reaction by breaking bonds
A Catalyst
Is a substance that increases the rate of a chemical reaction without being used up in the process. It increases the rate of reaction by providing an alternative route of lower activation energy
A Heterogeneous Catalyst
Is in a different phase from the reactants
A Homogeneous Catalyst
Is in the same phase as the reactants
Hydrocarbon
Compound of Carbon and Hydrogen only
Functional Group
Atom/group of atoms that gives the compound it’s characteristics properties
Saturated Compound
One that contains no C to C multiple bonds
Unsaturated Compound
One that contains C to C multiple bonds
Empirical Formula
Formula of a compound with the atoms of the element in their simplest ratio
Structural Isomers
Compounds with the same molecular formula but a different structural formula, e.g arrangement of the atoms
E-Z Isomerism
Occurs in alkenes (and substituted alkenes) due to restricted rotation about the double bond
Van der Waals Forces
Dipole-Dipole or induced dipole-induced dipole interactions between atoms and molecules
Fossil Fuels
One that is derived from organisms that lived long ago
Non-renewable Resources
Those that cannot be reformed in a reasonable timescale
Greenhouse Gas
One that causes an increase in the Earth’s temperature
Acid Rain
Rain with lower than expected pH
Complete Combustion
Combustion that occurs with excess oxygen (creates CO)
Incomplete Combustion
Combustion that occurs with insufficient Oxygen (creates CO2)
Halogenation
Reaction with any halogen
Initiation
Reaction that starts the process
Homolytic Bond Fission
When a bond is broken and each of the bonded atoms receive one of the bonded electrons
Radical
Species with an unpaired electron
Propagation
Reaction by which the process continues/grows
Chain Reaction
One that involves a series of steps and once started continues
Termination
Reaction that ends the process
Reaction Mechanism
Shows stages by which a reaction proceeds
Substitution Reaction
Is one in which one atom/group is replaced by another atom/group
Pie Bond
One formed by the sideways overlap of p shell elections
Electrophile
Electron deficient species that can accept a lone pair of electrons
Heterolytic Bond Fission
When a bond is broken and one of the bonded atoms receives both the bonded electrons
Addition Reaction
Reaction in which reagents combine to give one product
Carbocation (Carbonium Ion)
Positively charged carbon - containing species
Polymerisation
Is the joining of a very large number of monomer molecules to make a large polymer molecule
Monomer
Is a small molecule that can be made into a polymer
Polymer
Is a large molecule made by joining many monomer molecules
Repeat Unit
The section of the polymer that is repeated to make the whole structure
Halogenoalkanes
Homologous series in which one or more hydrogen atoms in an alkane have been replaced by a halogen
Hydrolysis
Reaction with water to produce a new product
Nucleophile
Species with a lone pair of electrons that can be donated to an electron deficient centre
Substitution Reaction
Reaction in which one atom/group is replaced by another
Elimination Reaction
One that involves the loss of a small molecule to produce double bonds
CFCs
Halogenoalkanes containing both chlorine and fluorine
HFCs
Halogenoalkanes containing fluorine as the only halogen
Ozone Layer
Layer around the earth containing O3 molecules
Alcohol
An homologous series containing -OH as the functional group
Fermentation
Enzyme-catalysed reaction that converts sugars to ethonal
Biofuel
Fuel that has been produced using a biological source
Carboxylic Acid
An homologous series containing -COOH as the functional group
Weak Acid
An acid that only partially ionises in aqueous solution
Fragmentation
Splitting of molecules in a mass spectrometer into smaller parts
Molecular Ion
Positive ion formed from in the mass spectrometer from the whole molecule
Wavenumber
Measure of energy absorbed, used in IR spectra
Characteristic Adsorption
Wavenumber range at which a particular bond absorbs radiation
Chemical Shift
Measure of difference in parts/million, from the standard of the energy of a particular absorption type
Environment
Nature of the surrounding atoms/groups in a molecule
