Unit 2 Definitions Flashcards
Empirical formula
A formula which shows the simplest whole number ratios of each element in a compound
Molecular formula
A formula which shows the actual number of atoms of each element in a molecule
Molar gas volume
The volume of one mole of gas under specified conditions of temperature and pressure
Avogadro’s law
The volume of one mole of gas is exactly 24dm^3 if measured at one atmospheric pressure and 20°C
Hydrocarbon
A compound that is made of carbon and hydrogen only
Saturated
A compound with no C=C bonds
Unsaturated
A compound with one or more C=C bonds
Homologous series
Compounds that have the same general formula, similar chemical properties, show a graduation in physical properties and successive numbers differ by a CH2 unit
Functional groups
The reactive group within a compound
Structural isomers
Molecules with the same molecular formula but with different structural formula
Functional isomers
Compounds that have the same molecular formula but a different structural formula with different functional groups
Geometric isomers
Molecules with the same structural formula, but different arrangement of atoms due to the presence of one or more C=C bonds
Substitution
Replacing one atom/group with a different atom/group
Radical
A particle with an unpaired electron
Homolytic fission
Bond breaking in which one of the shared electrons goes to each atom
Heterolytic fission
Bond breaking in which both of the electrons in the shared pair go to a single atom
Sigma bond
A covalent bond formed by the linear overlap of atomic orbitals
Pi bond
A covalent bond formed by the sideways overlap of p orbitals
Bond length
The distance between the nuclei of two covalently bonded atoms
Hydrogenation
Addition of a hydrogen molecule across a C=C bond
Electrophile
An ion or molecule that attacks a region of high electron density
Heterolytic fission
Bond breaking in which both electrons in the shared pair go to a single atom
Monomers
Many small molecules which can join together to form a polymer
Polymer
Large molecule formed when monomers join together
Polymerisation
Joining together of small molecules to form a large molecule
Nucleophile
An ion or molecule, with a lone pair of electrons, that attacks an area of low electron density
Miscibility
Liquids which mix in all proportions. Ie: form a single layer
Hydrolysis
Breaking up molecules by reaction with water
Ground state
A molecular vibration which is in its lowest possible energy state
Wave number
The reciprocal of wavelength (measured in cm/1
Endothermic
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants
Endothermic
A reaction in which t he enthalpy of the products is less than the enthalpy of the reactants
Activation energy
The minimum amount of energy required for a reaction to occur
Standard enthalpy change
Change in heat energy at constant constant pressure, measured at standard conditions
Enthalpy of formation
The enthalpy change when one mole of a compound is formed from its elements under standard conditions
Enthalpy of combustion
The enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions
Enthalpy of neutralisation
The enthalpy change when one mole of water is produced in a neutralisation reaction under standard conditions
Conservation of energy
Energy cannot be created or destroyed but it can change from one form to another
Hess’s law
The enthalpy change for a reaction is independent of the route taken, provided the i rial and final conditions are the same
Average bond enthalpy
The energy required to break one mole of a given bond, averaged over many compounds
Rate of reaction
The change in concentration of a reactant or product with respect to time
Catalyst
A substance which increases the rate of reaction without being used up itself
Activation energy
The minimum amount of energy required for a reaction to occur
Maxwell Boltzmann Distribution
The distribution of energies of molecules at a particular temperature, often shown on a graph.
Reversible
A reaction which goes in both the forward and backward directions
Dynamic
The rate of the forward reaction is equal to the rate of the backward reaction
Equilibrium
A reversible reaction in which the amount of each reactant/product remains constant
Homogeneous
A reaction in which all the reactants and products are in the same physical state
Heterogeneous
A reaction in which all the reactants and products aren’t in the same physical state
Le Chatilier’s principle
For a system to be at dynamic equilibrium, the system will move in the direction to oppose any external change imposed upon it
Heterogeneous catalyst
The catalyst is in a different phase from the reactants
S block element
An element which has an atom with the highest energy/outer electron in an s sub shell
Solubility
The maximum mass of solute that will dissolve in 100g of solvent at a stated temperature
