Definitions Flashcards
Electronegativity
The power of an atom to attract electron density in a covalent bond towards itself.
Activation energy
Minimum energy that a particle needs in order to react. The energy (enthalpy) difference between the reactants and the transition state.
Aldehyde
An organic compound with the general formula RCHO
Alkaline earth metals
Group 2
Alkane
Hydrocarbon with C-C and C-H single bonds only
Allotropes
Pure elements which can exist in different physical forms in which their atoms are arranged differently. E.g. Diamond, graphite and buckminsterfullerene
Atom economy
Describes the efficiency of a chemical reaction by comparing the total number of atoms in the product with the total number of atoms in the starting materials
Atomic orbital
Space around the atomic nucleus where there is a high probability of finding an electron
Avogadro constant
Number of particles in one mole of a substance
6.023 x 10(23)
Bond dissociation enthalpy
The enthalpy change required to break a covalent bond with all species in the gaseous state
Calorimeter
Instrument for measuring the heat changes that accompany chemical reactions
Catalytic cracking
The breaking, either the aid of a catalyst, of long-chain alkane molecules (from crude oil) into short chain hydrocarbons.
Catalyst
Substance that alters the rate of chemical reaction without being used up.
It provides an alternate pathway for the reaction that uses a lower activation energy.
Carbocation
An organic ion in which one carbon has a positive charge
Carbon-neutral
A process in which as much CO2 is absorbed as is released
Chemical feedstock
The starting materials in a industrial chemical process
Co-ordinate bonding
Covalent bonding in which both the electrons in the bond come from one atom
Covalent bond
2 electron pairs shared between two atoms in a bond
Displacement reaction
Reaction in which an atom replaces another in a compound
Disproportionation
Redox reaction in which the oxidation number of some atoms of a particular element increases and that of other atoms of the same element decreases
Electron pair repulsion theory
Explains the shapes of simple molecules by assuming pairs of electrons around a central atom repel each other and take up positions as far away as possible from each other in space
Electrophile
Electron-deficient atom,ion or molecule that takes part in an organic reaction by attacking areas of high electron density in another reactant
Enthalpy change
Measure of heat energy given out or taken in when a chemical or physical change occurs at constant pressure
Finger print region
Area of an infra red spectrum below about 1500cm-1
Caused by complex vibrations of the whole molecule and is characteristic of a particular molecule
Ionisation energy
Energy required to remove a mole of electrons from a mole of isolated gaseous atoms or ions
Maxwell Boltzmann distribution
Distribution of energies of molecules in a gas or liquid
Oxidising agent
Reagent that accepts electrons
Reducing agent
Electron donor
Polar
Molecule with a non symmetrically disoriented charge
Positive inductive effect
Describes tendency of some atoms or groups of atoms to release electrons via a covalent bond
Specific heat capacity
Amount of heat need to raise the temperature of 1g of a substance by 1K
Standard molar enthalpy change of combustion
Enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in their standard states
Standard molar enthalpy change of formation
Enthalpy change when 1 mole of a substance is formed from its elements with all reactants and products in their standard states
Hess’s law
The enthalpy change for a chemical reaction is independent of the route taken
Me Châtelier’s principle
If a system at equilibrium is disturbed, the equilibrium moves in the direction that reduces the disturbance
Salt
Any chemical compound formed from the reaction between an acid an a base, with all or part of the hydrogen of the acid replaced by a metal or cation
Macromolecular
Giant molecule with covalent bonding
