definitions Flashcards
define relative atomic mass
the total number of protons and neutrons
define electronegativity
the power of an atom to attract an electron pair in a covalent bond
define enthalpy change
the change in heat energy in a chemical reaction at a constant pressure
define enthalpy of combstion
the enthalpy change when one mole of a substance is completely burnt in excess oxygen under their standard conditions, with all reactants and products in their standard states
define enthalpy of formation
the enthalpy change when one mole of a substance is formed from its constituent elements under standard conditions, with all reactants and products in their standard states
define mean bond enthalpy
the amount of energy required to break one mole of a covalent bond into gaseous atoms, averaged over a range of different compounds
define Hess’ law
that the enthalpy change for all chemical reactions is the same whatever route taken from reactants to products
define dynamic:
when the forward and backward reactions proceed at equal rates
define equilibrium:
when the concentration of reactants and products are at a constant
define first ionisation energy:
the amount of energy required to remove one mole of an atom in the gaseous state
