Thermodynamics

Question 1

Define Ionisation enthalpy (first + second)

• Exothermic or Endothermic?

Answer 1

• First: The enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions. (Endothermic)
• Second: The enthalpy change when each ion in one mole of gaseous 1+ ions loses one electron to form one mole of gaseous 2+ ions. (Endothermic)

Question 2

Define Electron affinity (first + second)

• Exothermic or Endothermic?

Answer 2

• First: The enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions. (Exothermic)
• Second: The enthalpy change when each ion in one mole of gaseous 1- ions gains one electron to form one mole of gaseous 2- ions. (Endothermic)

Question 3

Define Enthalpy of atomisation. (Exo/Endo?)

Answer 3

• The enthalpy change when one mole of gaseous atoms is produced from an element in its standard state.
  (Endothermic)

Question 4

Define Enthalpy of hydration. (Exo/Endo?)

Answer 4

• The enthalpy change when one mole of gaseous ions becomes hydrated.
  (Exothermic)

Question 5

Define Enthalpy of solution. (Exo/Endo?)

Answer 5

• The enthalpy change when one mole of an ionic solid dissolves in an amount of water large enough so that the dissolved ions are separated enough and don’t react with each other.

(Exo/Endo - varies)

Question 6

Define Bond dissociation enthalpy. (Exo/Endo?)

Answer 6

• The enthalpy change when one mole of covalent bonds is broken in the gaseous phase.
  (Endothermic)

Question 7

Define Lattice enthalpy of formation. (Exo/Endo?)

Answer 7

• The enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase.
  (Exothermic)

Question 8

Define Lattice enthalpy of dissociation. (Exo/Endo?)

Answer 8

• The enthalpy change when one mole of a solid ionic compound is broken up into its constituent elements in the gaseous phase.
  (Endothermic)

Question 9

Define Enthalpy of vapourisation. (Exo/Endo?)

Answer 9

• Enthalpy change when one mole of a liquid is turned into a gas.
  (Endothermic)

Question 10

Define Enthalpy of fusion. (Exo/Endo?)

Answer 10

• The enthalpy change when one mole of a solid is turned into a liquid.
  (Endothermic)

Question 11

Define Enthalpy of formation. (Exo/Endo?)

Answer 11

• The enthalpy change when one mole of a substance is formed from its constituent elements in standard states under standard conditions.
  (Exothermic)

Question 12

Define Enthalpy of combustion. (Exo/Endo?)

Answer 12

• The enthalpy change when one mole of a substance is burned completely with oxygen in standard states under standard conditions.

Question 13

Define Enthalpy Change

Answer 13

The heat energy of a reaction under constant pressure.

Question 14

Define Enthalpy Change

Answer 14

The heat energy of a reaction under constant pressure.