Thermodynamics A2 definitions

Question 1

enthalpy of formation

Answer 1

The enthalpy change when one mole of a compound is formed from its constituent elements in standard states under standard conditions

Question 2

enthalpy of combustion

Answer 2

The enthalpy change when one mole of substance is burned completely in oxygen in standard states and conditions

Question 3

enthalpy of atomisation

Answer 3

The enthalpy change of the formation of one mole of gaseous atoms from the element in its standard state under standard conditions.

Question 4

first ionisation energy

Answer 4

The enthalpy change when one mole of gaseous atoms loses an electron to form one mole of gaseous 1+ ions

Question 5

Second Ionisation Energy

Answer 5

The enthalpy change when one mole of gaseous 1+ ions loses an electron to form one mole of gaseous 2+ ions

Question 6

first electron affinity

Answer 6

Enthalpy change when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions.

Question 7

Second Electron Affinity

Answer 7

Enthalpy change when one electron is added to each ion in one mole of gaseous ions to form one mole of gaseous 2- ions

Question 8

Enthalpy of lattice formation

Answer 8

Enthalpy change when one mole of a solid ionic compound is formed from its gaseous ions.
(This is always negative)

Question 9

enthalpy of hydration

Answer 9

Enthalpy change when one mole of aqueous ions is formed from one mole of gaseous ions

Question 10

enthalpy of solution

Answer 10

Enthalpy change when one mole of ionic solid completely dissolves in enough solvent under standard conditions to form an infinitely dilute solution.

Question 11

Bond enthalpy

Answer 11

The amount of energy required to break one mole of a specific covalent bonterm-11d in the gas phase is called the bond dissociation energy

Question 12

mean bond enthalpy

Answer 12

The average value of the bond dissociation enthalpy for a given type of bond taken from a range of different compounds.

Question 13

lattice enthalpy of disassociation

Answer 13

The enthalpy change when one mole of solid ionic compound is dissociated into its gaseous ions.
(This is always positive)

Question 14

Define entropy

Answer 14

the disorder of a system

Question 15

enthalpy of solution

Answer 15

The enthalpy change of solution is the enthalpy change when 1 mole of an ionic substance dissolves in water to give a solution of infinite dilution

Question 16

enthalpy of hydration

Answer 16

The hydration enthalpy is the enthalpy change when 1 mole of gaseous ions dissolve in sufficient water to give an infinitely dilute solution. Hydration enthalpies are always negative.