Enthalpy change definitions

Question 1

Standard enthalpy of formation

Answer 1

Enthalpy change that occurs when one mole of a substance is formed from its elements with all the reactants and products in their standard states under standard conditions

Question 2

Standard enthalpy of combustion

Answer 2

Enthalpy change when one mole of a substance undergoes complete combustion in oxygen to form the products with all the reactants and products in their standard states under standard conditions

Question 3

Bond dissociation enthalpy

Answer 3

Enthalpy change to break one mole of a specific covalent bond to form two separate atoms with all the reactants and products in the gaseous state

Question 4

standard enthalpy change of neutralisation

Answer 4

Enthalpy change when one mole of aqueous hydrogen ions reacts with one mole of aqueous hydroxide ions to form one mole of water with all reactants and products in their standard states under standard conditions

Question 5

Standard enthalpy of atomisation

Answer 5

enthalpy change required to form one mole of gaseous atoms from the element in its standard state under standard conditions

Question 6

standard conditions

Answer 6

100kpa and a specified temperature (e.g. 298k)

Question 7

First ionisation energy

Answer 7

Enthalpy change required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous, singly positively charged ions

Question 8

Second ionisation energy

Answer 8

Enthalpy change required to remove one electron from each ion in one mole of gaseous, singly positively charged ions to form one mole of gaseous doubly positively charged ions

Question 9

second electron affinity

Answer 9

Enthalpy change required to add one electron to each ion in one mole of gaseous, singly negatively charged ions to form one mole of gaseous, doubly negatively charged ions

Question 9

First electron affinity

Answer 9

Enthalpy change when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous atoms to form one mole of gaseous, singly negatively charged ions

Question 10

Lattice (formation) enthalpy

Answer 10

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

Question 11

Lattice (dissociation) enthalpy

Answer 11

enthalpy change required to turn one mole of a solid ionic compound into its constituent ions in the gaseous state

Question 12

Enthalpy of hydration

Answer 12

enthalpy change when one mole of gaseous ions is dissolved to infinite dilution in water, forming hydrated ions

Question 13

Standard enthalpy of solution

Answer 13

Enthalpy change when one mole of solute is dissolved to infinite dilution in water, forming a solution with all the reactants and products in their standard states, under standard conditions.

Question 14

Enthalpy change that occurs when one mole of a substance is formed from its elements with all the reactants and products in their standard states under standard conditions

Answer 14

Standard enthalpy of formation

Question 15

Enthalpy change to break one mole of a specific covalent bond to form two separate atoms with all the reactants and products in the gaseous state

Answer 15

Bond dissociation enthalpy

Question 15

Enthalpy change when one mole of a substance undergoes complete combustion in oxygen to form the products with all the reactants and products in their standard states under standard conditions

Answer 15

Standard enthalpy of combustion

Question 16

Enthalpy change when one mole of aqueous hydrogen ions reacts with one mole of aqueous hydroxide ions to form one mole of water with all reactants and products in their standard states under standard conditions

Answer 16

standard enthalpy change of neutralisation

Question 17

enthalpy change required to form one mole of gaseous atoms from the element in its standard state under standard conditions

Answer 17

Standard enthalpy of atomisation

Question 18

Enthalpy change required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous, singly positively charged ions

Answer 18

First ionisation energy

Question 18

100kpa and a specified temperature (e.g. 298k)

Answer 18

standard conditions

Question 19

Enthalpy change required to remove one electron from each ion in one mole of gaseous, singly positively charged ions to form one mole of gaseous doubly positively charged ions

Answer 19

Second ionisation energy

Question 20

Enthalpy change when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous atoms to form one mole of gaseous, singly negatively charged ions

Answer 20

First electron affinity

Question 21

Enthalpy change required to add one electron to each ion in one mole of gaseous, singly negatively charged ions to form one mole of gaseous, doubly negatively charged ions

Answer 21

second electron affinity

Question 22

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

Answer 22

Lattice (formation) enthalpy

Question 23

enthalpy change required to turn one mole of a solid ionic compound into its constituent ions in the gaseous state

Answer 23

Lattice (dissociation) enthalpy

Question 24

enthalpy change when one mole of gaseous ions is dissolved to infinite dilution in water, forming hydrated ions

Answer 24

Enthalpy of hydration

Question 25

Enthalpy change when one mole of solute is dissolved to infinite dilution in water, forming a solution with all the reactants and products in their standard states, under standard conditions.

Answer 25

Standard enthalpy of solution

Question 26

H+(aq) + OH-(aq) —–> H2O(l)

Answer 26

Standard enthalpy change of neutralisation

Question 27

1/4 P4(s) —–> P(g)

Answer 27

Standard enthalpy of atomisation

Question 28

Mg(g) —–> Mg+(g) + e-

Answer 28

First ionisation energy

Question 29

Mg+(g) ——> Mg2+(g) + e-

Answer 29

Second ionisation energy

Question 30

Ca(s) + C(graphite)(s) + 1.5O2(g) —-> CaCO3(s)

Answer 30

Standard enthalpy of formation

Question 31

C2H6(g) + 3.5O2(g) —–> 2CO2(g) + 3H2O(l)

Answer 31

Standard enthalpy of combustion

Question 32

O2(g) —-> O(g) + O(g)

Answer 32

Bond dissociation enthalpy (Bond enthalpy)

Question 33

O(g) + e- —-> O-(g)

Answer 33

First electron affinity

Question 34

O-(g) + e- —–> O2-(g)

Answer 34

Second electron affinity

Question 35

2Al 3+ (g) + 3O2-(g) —-> Al2O3

Answer 35

Lattice (formation) enthalpy

Question 36

Al2O3 (s) —-> 2Al3+ (g) + 3O2- (g)

Answer 36

Lattice (dissociation) enthalpy

Question 37

Al3+(g) + aq —-> Al3+ (aq)

Answer 37

Enthalpy of hydration

Question 38

NaCl(s) + aq —-> Na+(aq) + Cl-(aq)

Answer 38

Standard enthalpy of solution