Enthalpy definitions

Question 1

standard enthalpy of formation

Answer 1

enthalpy change when one mole of compoung is formed from its constituent elements under standard conditions, all reactants and products in their standard states

Question 2

standard enthalpy of combustion

Answer 2

enthalpy change when one mole of substance is completely burnt in oxygen

Question 3

standard enthalpy of atomisation

Answer 3

enthalpy change when one mole of gaseous atoms is formed from the element in its standard state under standard conditions

Question 4

first ionisation energy

Answer 4

standard enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single positive charge

Question 5

second ionisation energy

Answer 5

loss of a mole of electrons from a mole of singly positive charged ions

Question 6

first electron affinity

Answer 6

standard enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single negative charge

Question 7

second electron affinity

Answer 7

enthalpy change when mole of electrons is added to a mole of gaseous ions each with a single negative charge to form ions each with two neative charges

Question 8

lattice enthalpy of formation

Answer 8

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

Question 9

lattice enthalpy of dissociation

Answer 9

standard enthalpy change when one mole of solid ionic compound is dissociated into its gaseous ions

Question 10

enthalpy of hydration

Answer 10

standard enthalpy change when water molecules surround one mole of gaseous ions

Question 11

enthalpy of solution

Answer 11

standard enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far enough apart not to interact with each other

Question 12

mean bond enthalpy

Answer 12

enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form two free radicals, averaged over a range of compounds