Energy

Question 1

LATTICE ENTHALPY

Answer 1

The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions.
It is always exothermic/negative.

Question 2

ENTHALPY CHANGE OF SOLUTION

Answer 2

The enthalpy change that takes place when one mole of a compound is completely dissolved in water.

Question 3

ENTHALPY CHANGE OF HYDRATION

Answer 3

The enthalpy change that takes place when one mole of gaseous ions is dissolved in water forming one mole of aqueous ions.

Question 4

ENTHALPY CHANGE OF FORMATION

Answer 4

The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states, under standard conditions.

Question 5

FIRST IONISATION ENERGY

Answer 5

The enthalpy change accompanying the removal of one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1⁺ ions.

Question 6

SECOND IONISATION ENERGY

Answer 6

The enthalpy change accompanying the removal of one electron from each ion in one mole of gaseous 1⁺ ions to form one mole of gaseous 2⁺ ions.

Question 7

ENTHALPY CHANGE OF ATOMISATION

Answer 7

The enthalpy change that takes place when one mole of gaseous atoms forms from the element in its standard state.

Question 8

FIRST ELECTRON AFFINITY

Answer 8

The enthalpy change accompanying the addition of one electron to each atom in one mole of gaseous atoms to form one mole of gaseous 1⁻ ions.

Question 9

SECOND ELECTRON AFFINITY

Answer 9

The enthalpy change accompanying the addition of one electron to each ion in one mole of gaseous 1⁻ ions to form one mole of gaseous 2⁻ ions.

Question 10

Factors that affect lattice enthaply

Answer 10

Stronger ionic bonds when
• smaller ionic radius
• greater ionic charge
• stronger electrostatic forces of attraction (between oppositely charged ions)
• more exothermic/negative lattice enthaly

Question 11

Factors that affect enthalpy change of hydration

Answer 11

Enthalpy change of hydration of ions is more exothermic when ions have:
• smaller ionic radius
• greater ionic charge
• stronger electrostatic forces of attraction between ions and polar water molecules
• more exothermic/negative hydration enthaly

Question 12

Calculating enthalpy change

Answer 12

Q=mcΔT in J

ΔH=Q in KJ/mol of one acid

Question 13

Why is ΔH positive?

Answer 13

Because intermolecular forces have to be broken & this requires energy