Chemistry A2 Chapter 22 - Enthalpy and Entropy

Question 1

Lattice enthalpy

Answer 1

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

Question 2

Standard enthalpy change of formation

Answer 2

The enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions with all reactants and products in their standard states

Question 3

Standard enthalpy change of atomisation

Answer 3

The enthalpy change that takes place for the formation of one mole of gaseous atoms from the element in its standard state under standard conditions

Question 4

Why is the standard enthalpy change of atomisation always endothermic?

Answer 4

Bonds are broken to form gaseous atoms

Question 5

First ionisation energy

Answer 5

The enthalpy change/energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 6

First electron affinity

Answer 6

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 7

Standard enthalpy change of solution

Answer 7

The enthalpy change that takes place when one mole of a solute dissolves in a solvent

Question 8

The enthalpy change of hydration

Answer 8

The enthalpy change that accompanies the dissolving of gaseous ions in water to form one mole of aqueous ions

Question 9

Why are ionisation energies endothermic?

Answer 9

Energy is required to overcome the attraction between the negative electron and positive nucleus

Question 10

Why are first electron affinities exothermic?

Answer 10

The electron being added is attracted towards the nucleus

Question 11

Why are second electron affinities endothermic?

Answer 11

A second electron is being gained by a negative ion and so will initially be repelled meaning energy must be put in to force the electron onto the negative ion