topic 15.1 - Energy cycles

Question 1

Enthalpy of solution

Answer 1

Enthalpy change when one mole of a compound is dissolved in excess solvent to form aqueous ions (can be exothermic or endothermic)

NH₄Cl (s) -> NH₄⁺ (aq) + Cl⁻ (aq)

∆H (sol) = ∆H (hyd) + ∆H (lat)

Question 2

Enthalpy of hydration

Answer 2

The enthalpy change when one mole of gaseous ions form aqueous ions in the presence of water

Na⁺ (g) + Cl⁻ (g) -> Na⁺ (aq) + Cl⁻ (aq)

∆H (sol) - ∆H (lat) = ∆H (hyd)

Question 3

Lattice enthalpy

Answer 3

The enthalpy change when one mole of a solid ionic lattice is converted into its gaseous ions (always endothermic)

NaCl (s) -> Na⁺ (g) + Cl⁻ (g)

∆H (sol) - ∆H (hyd) = ∆H (lat)

Question 4

Enthalpy of atomisation

Answer 4

The enthalpy change when one mole of separated gaseous is formed from its standard state

Na (s) -> Na (g) // 1/2Cl₂ (g) -> Cl (g)

Question 5

First ionisation energy

Answer 5

The energy required to remove one mole of electrons from one mole of gaseous atoms

Na (g) -> Na⁺ (g) + e⁻

Question 6

Second ionisation energy

Answer 6

The energy required to remove one mole of electrons from one mole of gaseous 1⁺ ions

Mg⁺ (g) -> Mg²⁺ (g) + e⁻

Question 7

First electron affinity

Answer 7

The enthalpy change when one mole of electrons is added to one mole of gaseous atoms

O (g) + e⁻-> O⁻ (g)

Question 8

Second electron affinity

Answer 8

The enthalpy change when one mole of electrons is added to one mole of gaseous 1⁻ ions

O⁻ (g) + e⁻-> O²⁻ (g)