ENTHALPY ; Lattice enthalpy : Born Haber Cycles

Question 1

standard enthalpy change of formation

Answer 1

the enthalpy change that takes place when one mole of a compound is formed from it’s elements under standard conditions, with all reactants and products in their standard states.

Question 2

standard enthalpy change of atomisation

Answer 2

the enthalpy change that takes place when one mole of a gaseous atom is formed from the element in its standard state under standard conditions.

Question 3

lattice enthalpy

Answer 3

the change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.

Question 4

first ionisation energy

Answer 4

the enthalpy change required to remove one electron from each atom in one mole of gaseous atoms to from one mole of gaseous 1+ ions

Question 5

first electron affinity

Answer 5

the enthalpy change that takes place when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous -1 ions.

Question 6

bond enthalpy

Answer 6

The energy needed to break one mole of a given bond in a gaseous molecule. The units are kJ mol–1 (kilojoules per mole).

Question 7

sublimation

Answer 7

the transition of a substance directly from the solid to the gas state, without passing through the liquid state

Question 8

entropy

Answer 8

The quantitative measure of the degree of disorder in a system.

Question 9

standard entropy.

Answer 9

Standard entropy of reaction. The entropy change that accompanies a reaction in the molar quantities expressed in a chemical reaction under standard conditions, all reactants and products being in their standard states

Question 10

standard conditions of standard enthalpy of raction?

Answer 10

• 298 k

- 100kPa

Question 11

difference between entropy and enthalpy ?

Answer 11

Entropy is thus a measure of the random activity in a system, whereas enthalpy is a measure of the overall amount of energy in the system.