2. Thermodynamics Definitions

Question 1

Define Enthalpy of Formation

Answer 1

Enthalpy change when 1 mole of a substance is formed from its constituent elements with all substances in their standard states.

Question 2

Is Enthalpy of Formation endo or exothermic?

Answer 2

exothermic (-ive) for most substances

Question 3

Define Enthalpy of Combustion

Answer 3

Enthalpy change when 1 mole of a substance undergoes complete combustion in oxygen with all substances in their standard states

Question 4

Is Enthalpy of Combustion endo or exothermic?

Answer 4

Exothermic (-ive)

Question 5

Define Enthalpy of Neutralisation

Answer 5

Enthalpy change when 1 mole of water is formed in a reaction between an acid and alkali under standard conditions

Question 6

Is enthalpy of neutralisation endo or exothermic?

Answer 6

Exothermic (-ive)

Question 7

Define first ionisation energy

Answer 7

Enthalpy change when each atom in 1 mole of gaseous atoms loses one electron to form 1 mole of gaseous 1+ ions

Question 8

Is ionisation energy endo or exothermic?

Answer 8

Endothermic (+ive)

Question 9

First ionisation energy of Mg?

Answer 9

Mg(g) –> Mg+(g) + e-

Question 10

Define second ionisation energy

Answer 10

Enthalpy change when each atom in 1 mole of gaseous 1+ ions loses 1 electron to form 1 mole of gaseous 2+ ions

Question 11

Second ionisation energy of Mg?

Answer 11

Mg+(g) —> Mg2+(g) + e-

Question 12

Define first electron affinity

Answer 12

Enthalpy change when each atom in 1 mole of gaseous atoms gains 1 electron to form 1 mole of gaseous 1- ions

Question 13

Is first electron affinity endo or exothermic?

Answer 13

Exothermic (-ive) for many non-metals

Question 14

First electron affinity of O2?

Answer 14

O(g) + e- —> O-(g)

Question 15

Define second electron affinity

Answer 15

Enthalpy change when each atom in 1 mole of gaseous 1- ions gains 1 electron to form 1 mole of gaseous 2- ions

Question 16

Is second electron affinity endo or exothermic?

Answer 16

Endothermic (+ive) as adding -ive electron to -ive ion

Question 17

Second electron affinity of O2?

Answer 17

O-(g) + e- —> O^2-

Question 18

Define enthalpy of atomisation

Answer 18

Enthalpy change when 1 mole of gaseous atoms is produced from an element in its standard state

Question 19

Is enthalpy of atomisation endo or exothermic?

Answer 19

Endothermic (+ive)

Question 20

Enthalpy of atomisation of iodine?

Answer 20

1/2 I2(s) —-> I(g)

Question 21

Define hydration enthalpy

Answer 21

Enthalpy change when 1 mole of gaseous ions become hydrated (dissolved in water)

Question 22

Is hydration enthalpy endo or exothermic?

Answer 22

Exothermic (-ive)

Question 23

Hydration enthalpy of Mg ions?

Answer 23

Mg^2+(g) + aq —> Mg^2+(aq)

Question 24

Define enthalpy of solution

Answer 24

Enthalpy change when 1 mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are well separated and do not interact with each other

Question 25

Is enthalpy of solution endo or exothermic?

Answer 25

Varies`

Question 26

Enthalpy of solution of Magnesium Chloride?

Answer 26

MgCl2(s) + aq ----> Mg^2+(aq) + 2Cl^(aq)

Question 27

Define bond dissociation enthalpy

Answer 27

Enthalpy change when 1 mole of covalent bonds is broken in the gaseous state

Question 28

Is bond dissociation enthalpy endo or exothermic?

Answer 28

Endothermic (+ive)

Question 29

Bond dissociation enthalpy of I-I bond?

Answer 29

I2(g) ---> 2I(g)

Question 30

Define lattice enthalpy of formation

Answer 30

Enthalpy change when 1 mole of a solid ionic compound is formed from its constituent ions in the gas phase

Question 31

Is lattice enthalpy of formation endo or exothermic?

Answer 31

Exothermic (-ive)

Question 32

Lattice enthalpy of formation of magnesium chloride?

Answer 32

Mg^2+(g) + 2Cl^-(g) ----> MgCl2(s)

Question 33

Define lattice enthalpy of dissociation

Answer 33

Enthalpy change when 1 mole of a solid ionic compound is broken up into its constituent ions in the gas phase

Question 34

Is lattice enthalpy of dissociation endo or exothermic?

Answer 34

Endothermic (+ive)

Question 35

Lattice enthalpy of dissociation of magnesium chloride?

Answer 35

MgCl2(s) ----> Mg^2+(g) + 2Cl^-(g)

Question 36

Define enthalpy of vaporisation

Answer 36

Enthalpy change when 1 mole of a liquid is turned into a gas

Question 37

Is enthalpy of vaporisation endo or exothermic?

Answer 37

Endothermic (+ive)

Question 38

Enthalpy of vaporisation of water?

Answer 38

H2O(l) -----> H2O(g)

Question 39

Define enthalpy of fusion

Answer 39

Enthalpy change when 1 mole of a solid is turned into a liquid

Question 40

Is enthalpy of fusion endo or exothermic?

Answer 40

Endothermic (+ive)

Question 41

Enthalpy of fusion of Magnesium?

Answer 41

Mg(s) ----> Mg(l)