Thermodynamics: Born-Haber Cycles - Types of Enthalpies

Question 1

Define the term lattice enthalpy of formation

Answer 1

• ∆HLFEθ

- Enthalpy change when one mole of solid ionic lattice is formed from its gaseous ions

Question 2

Define the term lattice enthalpy of dissociation

Answer 2

• ∆HLDEθ

- Enthalpy change when one mole of solid ionic lattice is dissociated into its gaseous ions

Question 3

Define the term standard enthalpy of formation

Answer 3

• ∆Hfθ
• Enthalpy change when one mole of a compound is formed from its constituent elements
• With all substances in their standard states under standard conditions

Question 4

Define the term standard enthalpy of combustion

Answer 4

• ∆Hcθ
• Enthalpy change when one mole of a substance undergoes complete combustion in excess oxygen
• With all substances in their standard states under standard conditions

Question 5

Define the term enthalpy of atomisation

Answer 5

• ∆Hatθ
• Enthalpy change when 1 mole of gaseous atoms are formed from the element
• In its standard state under standard conditions

Question 6

Define the term ionisation energy

Answer 6

• ∆HIE1θ

- Enthalpy change when 1 mole of electrons is removed from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 7

Define the term second ionisation energy

Answer 7

• ∆HIE2θ

- Enthalpy change when 1 mole of electrons is removed from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions

Question 8

Define the term enthalpy of electron affinity

Answer 8

• ∆HEA1θ

- Enthalpy change when 1 mole of electrons are added to 1 mole of gaseous atoms to form 1 mole of gaseous 1- ions

Question 9

Define the term enthalpy of second electron affinity

Answer 9

• ∆HEA2θ

- Enthalpy change when 1 mole of electrons are added to 1 mole of gaseous 1- ions to form 1 mole of gaseous 2- ions

Question 10

Define the term bond dissociation enthalpy

Answer 10

• ∆HBDEθ

- Enthalpy change for breaking 1 mole of a particular covalent bond in the gaseous state

Question 11

Define the term enthalpy of solution

Answer 11

• ∆Ηsol°
• Enthalpy change when one mole of a solid ionic compound is dissolved in enough solvent to form an infinitely dilute solution
• Infinitely dilute solution is when a solution contains so much solvent, that adding more doesn’t change the concentration

Question 12

Define the term enthalpy of hydration

Answer 12

• ∆Ηhyd°

- Enthalpy change when one mole of gaseous ions is converted to one mole of aqueous ions

Question 13

Is standard enthalpy of formation exothermic or endothermic and why?

Answer 13

• Usually exothermic

- Bonds are being made

Question 14

Is standard enthalpy of combustion exothermic or endothermic and why?

Answer 14

• Always exothermic

- Bonds are being made

Question 15

Is ionisation energy exothermic or endothermic and why?

Answer 15

• Always endothermic

- Energy required to overcome the electrostatic attractive force between the nucleus and the electron

Question 16

Is the second ionisation energy exothermic or endothermic? Is it larger than the first ionisation energy?

Answer 16

• Always a larger endothermic process than first ionisation energy
• More energy needed to overcome electrostatic attractive force between positive ion and electron
• Electrons are closer to nucleus of ion

Question 17

Is enthalpy of atomisation exothermic or endothermic and why?

Answer 17

• Always endothermic

- Bonds are being broken

Question 18

Is enthalpy of first electron affinity exothermic or endothermic?

Answer 18

• Always exothermic
• Energy released when the nucleus attracts the the additional electron is larger than the energy absorbed to overcome inter-electronic repulsion i.e net attraction between atom and added electron

Question 19

Is enthalpy of second and successive electron affinities exothermic or endothermic?

Answer 19

• Always successively larger endothermic process

- Energy need to overcome repulsion between negative ions and the added electron

Question 20

Is bond dissocation enthalpy exothermic or endothermic and why?

Answer 20

• Always endothermic

- Bonds are being broken

Question 21

Is lattice formation enthalpy exothermic or endothermic and why?

Answer 21

• Always exothermic

- Ionic bonds being made between ions

Question 22

Is lattice dissociation endothermic or exothermic and why?

Answer 22

• Always endothermic

- Ionic bonds are being broken

Question 23

Is enthalpy change of solution exothermic or endothermic and why?

Answer 23

• Either

Question 24

Is enthalpy change of hydration exothermic or endothermic and why?

Answer 24

• Always exothermic

- Water molecules bond with ions