Terms in this set (25)
Isotopes are atoms of an element with the normal number of protons and electrons, but different numbers of neutrons. Isotopes have the same atomic number, but different mass numbers.
Time of flight mass spectrometer
1) Electrospray ionisation- produce gaseous charged ions using high voltage
2)Acceleration- electric fiels gives all ions same kinetic energy
2)Ion drift- flight tube where ions are seperated basd on different velocities
3)Ion detection- positive ions cause small electric current
5)Data analysis- mass spectrum plot of relative abundance against mass to charge ratio
Relative isotopic mass
The mass of a single isotope of an element relative to 1/12 of the mass of an atom of carbon-12.
Relative atomic mass
the average mass of an atom of an element relative to a 1/12 the mass of an atom of carbon 12.
when a molecule breaks up in mass spectrometer
first ionisation energy
the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
Relative molecular mass
the mass of a molecule relative to 1/12 the mass of an atom of carbon-12.
Ionic bonding involves electrostatic attraction between oppositely charged ions in a lattice
A co-ordinate (dative covalent) bond contains a shared pair of electrons with both electrons supplied by one atom.
the power of an atom to attract the pair of electrons in a covalent bond.
Enthalpy change (∆H)
the heat energy change measured under conditions of constant pressure.
standard enthalpy of combustion (∆c
the enthalpy change when 1 mole of a substance is burned completely in excess oxygen with all reactants and products in their standard conditions.
standard enthalpy of formation (∆f
when 1 mole of a compound is formed from its constituent elements with all reactants and products in standard states and standard conditions.
the enthalpy change for a chemical reaction is independent of the route taken and depends only on the final and initial states.
Mean bond enthalpy
a measure of energy required to break one mole of a covalent bond measures in the gaseous state in kJmol-1.
the minimum amount of energy which the reacting particles require for a successful collision.
Rate of reaction
the change in concentration of a reactant or product in a given period of time
A catalyst is a substance that increases the rate of a chemical reaction without being changed in chemical composition or amount. Catalysts work by providing an alternative reaction route of
lower activation energy.
reversible reaction at equilibrium:
• forward and reverse reactions proceed at equal rates
• the concentrations of reactants and products remain constant.
Le Chatelier's principle
if a factor is changed which affects a system in equilibrium, the position of equilibrium will move in a direction so as to oppose the change
Order of reaction
the power to which the concentration if this reactant is raised in the rate equation
the proportionality constant which links the rate of reaction to the concentrations in the rate equation.
Compounds that have the same molecular formula but a different structural formula.
Molecules which have the same molecular and structural formula but a different arrangement of atoms in 3D space.
Any fuel made from living organisms or their waste