Enthalpy change definitions

Question 1

Enthalpy change

Answer 1

the heat energy change at constant pressure

Question 2

standard enthalpy of formation

Answer 2

enthalpy change when one mole of a substance is formed from its elements under standard conditions, with all substances in their standard state

Question 3

standard enthalpy of combustion

Answer 3

enthalpy change when one mole of substance is completely combusted in excess oxygen under standard conditions, with all substances in their standard state

Question 4

mean bond enthalpy

Answer 4

enthalpy change when one mole of a given covalent bond is broken, averaged over a range of compounds

Question 5

bond dissociation enthalpy

Answer 5

enthalpy change to break the bond in one mole of gaseous molecules to form gaseous atoms

Question 6

standard enthalpy of atomisation

Answer 6

enthalpy change for the formation of one mole of gaseous atoms from the electrons in its standard state

Question 7

first ionisation energy

Answer 7

enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 8

second ionisation energy

Answer 8

enthalpy change when one mole of electrons is removed from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

Question 9

first electron affinity

Answer 9

enthalpy change when one mole of electrons is added to one mole of gaseous atoms to form one mole of gaseous 1- ions

Question 10

second electron affinity

Answer 10

enthalpy change when one mole of electrons is added to one mole of gaseous 1- ions, to form one mole of gaseous 2- ions

Question 11

lattice formation enthalpy

Answer 11

enthalpy change when one mole of a solid ionic compound is formed from its gaseous ions

Question 12

lattice dissociation enthalpy

Answer 12

enthalpy change to separate one mole of solid ionic compound into its gaseous ions