Energetics HL

Question 1

Define ionisation energy

Answer 1

the minimum amount of energy required to remove 1 mole of electrons from 1 mole of gaseous atoms

Question 2

What type of reaction is the ionisation energy of an element

Answer 2

endothermic reaction (energy is needed to overcome the attraction between the nucleus and the electron)

Question 3

Define enthalpy of atomisation

Answer 3

the enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state

Question 4

What types of reaction is the enthalpy of atomisation

Answer 4

endothermic

Question 5

What is the general equation of ionisation energy

Answer 5

X(n-1) (g) → X(n)+(g) +e-

Question 6

What is the general equation of enthalpy of atomisation

Answer 6

X (s) → X (g)

Question 7

Define lattice enthalpy

Answer 7

the enthalpy change when 1 mole of a solid ionic compound is separated into its gaseous ions under STP

Question 8

What type of reaction is lattice enthalpy

Answer 8

Exothermic

Question 9

What is the general equation of lattice enthalpy

Answer 9

XY (s) → X- (g) + S+ (g)

Question 10

Define electron affinity

Answer 10

the enthalpy change when 1 mole of electrons are added to 1 mole of gaseous atoms

Question 11

What type of reaction is electron affinity

Answer 11

exothermic

Question 12

What is the general equation of electron affinity

Answer 12

X(n-1- (g) + e- → X(n)-

Question 13

Define bond dissociation enthalpy

Answer 13

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

Question 14

What type of reaction is bond dissociation enthalpy

Answer 14

endothermic

Question 15

What is the general equation of bond dissociation enthalpy

Answer 15

X2 (g) → 2X (g)

Question 16

Define enthalpy of solution

Answer 16

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

Question 17

Define enthalpy of hydration

Answer 17

the enthalpy change when 1 mole of gaseous ions dissolve in water to give a solution of infinite dilution

Question 18

The general equation of enthalpy of solution

Answer 18

XY (s) → XY (aq)

Question 19

The general equation of enthalpy of hydration

Answer 19

X- (g) → X- (aq)

Question 20

What type of reaction is enthalpy of solution

Answer 20

exothermic or endothermic

Question 21

What type of reaction is enthalpy of hydration

Answer 21

exothermic

Question 22

What are the steps to the Born-Haber cycle

Answer 22

1) enthalpy change of atomisation (formation of gaseous atoms from elements)
2) ionisation energy (formation of metal gaseous ions)
3) electron affinity (formation of non-metal gaseous ions)
4) enthalpy of formation
5) lattice enthalpy

Question 23

What is the equation to find the lattice enthalpy

Answer 23

ΔHlatꝋ = ΔHfꝋ - ΔH1ꝋ

Question 24

What factors affect lattice enthalpy

Answer 24

• ionic charge
• the size of the ionic radius

Question 25

Explain why the size of the ionic radius affects the lattice enthalpy

Answer 25

• larger ionic radius decreases the electrostatic attraction in the lattice and result in a more negative (exothermic) lattice enthalpy

Question 26

Explain the effect of the ionic charge on the lattice enthalpy

Answer 26

An increase in ionic charge, results in a stronger force of electrostatic attraction and leads to a more positive (endothermic) lattice enthalpy

Question 27

What is the equation enthalpy of solution

Answer 27

ΔHsolꝋ = ΔHlatꝋ + ΔHhydꝋ

Question 28

What are the factors that affect the strength of the enthalpy of hydration

Answer 28

• the size of the ionic radius (smaller → greater attraction → more exothermic)
• the charge of the ion (greater charge → greater attraction → more exothermic)

Question 29

What happens when an ionic solid dissolves in water

Answer 29

water is polar, which means it will form ion-dipole bonds with the ions present in the solution
- O2 will be attracted to the positive ions and H2 will be attracted to the negative ions