Definitions Flashcards
Define: Enthalpy change
Give the symbol
Heat energy change measured under conditions of constant pressure.
Define: Standard enthalpy of combustion
Give the symbol
The enthalpy change when one mole of a substance is burnt completely in oxygen in standard conditions. All reactants and products are in their standard states.
Define: Standard enthalpy of formation
Give the symbol
The enthalpy change when one mole of a compound is formed from its constituent elements in standard conditions. All products and reactants are in their standard states.
Define: Mean bond enthalpy
The enthalpy change when one mole of covalent bonds in a gaseous molecule are broken. It is an average over many different molecules.
State Hess’ Law
The enthalpy change for a reaction is independent of the route taken from reactants to products.
Define: Hetereogenous catalyst
A catalyst that is in a different phase to the reactants.
Define: Homogenous catalyst
A catalyst that is the same phase as the reactants.
Define: Activation energy
The minimum energy required for a reaction to occur.
Define: Transition state
The species at the top of the curve on an enthalpy level diagram
Define: Rate of reaction
Change in concentraion per unit time.
Define: Dynamic Equilibrium
Rate of forward reaction = Rate of backward reaction
Concentrations of reactants and products are constant
Define: Catalyst
A substance that provides an alternative reaction pathway of lower activation energy.
OR
A substance that increase the rate of reaction and is chemically unchanged when the reaction has finished.
Define: Disproportionation reaction
A reaction where the same species is both oxidised and reduced.
Define: Polymerisation
Joining monomers to form long chains.
Define: Carbon neutral
An activity where there is no net carbon emissions to the atmosphere.
Define: Elastic collision
Collisions in which energy is transferred between molecules but no energy is lost.
Define: Hydration
Addition of water to a molecule.
Define: Hydrolysis
Breaking of a molecule by addition of water.
Define: Molecular ion
The molecule with a single positive charge.
State Le Chatlier’s Principle
When a system is in equilibrium, the position of equilibrium will shift such as to oppose the change introduced to the system.
Define: Brønsted-Lowry acid
Proton donor
Define: Brønsted-Lowry base
Proton acceptor
Define: Buffer solution
A solution that is resistant to changes in pH when small amounts of acid/alkali are added
Define: Structural isomerism
Same molecular formula but different structural formula
Define: Stereoisomerism
Same structural formula but different arrangement of atoms in space
Define: Complex ion
Central metal ion surrounded by ligands
Define: Ligand
Electron pair donor which forms coordinate bond(s) with a central metal ion
Define: Coordination number
The number of coordinate bonds to the central metal ion
Define: Lewis acid
Electron pair acceptor
Define: Lewis base
Electron pair donor
Define: Lattice enthalpy of dissociation
Give the symbol
The enthalpy change when one mole of a compound is from from its gaseous ions.
Define: Lattice dissociation enthalpy
Give the symbol
The enthalpy change when 1 mole of a compound is completely dissociatedinto itsgaseous ions.
Define: Enthalpy of atomisation
Give the symbol
The enthalpy change when 1 mole of gaseous atoms are from a substance in its standard state.
Define: First ionisation energy
Give the symbol
The enthalpy change when 1 mole of electrons are removed from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a single postive charge.
Define: First electron affinity
Give the symbol
The enthalpy change when 1 mole of electrons are added to 1 mole of gaseous atoms to form 1 mole of gaseous ions with a single negative charge.
Define: Enthalpy of hydration
Give the symbol
The enthalpy change when one mole of gaseous ions are dissolved in water to form one mole of aqueous ions.
Define: Enthalpy of solution
Give the symbol
The enthalpy change when one mole of a compound is dissolve in suffient solvent such that there is no further enthalpy change.
