Thermodynamics - Definitions

Question 1

Enthalpy change

Answer 1

Heat energy change at constant pressure

Question 2

Standard conditions

Answer 2

298 K
100 kPa
1 mol dm^-3

Question 3

Enthalpy of lattice dissociation, ∆H˚LD

Answer 3

Enthalpy change to separate one mole of a solid ionic compound into its gaseous ions

Question 4

Enthalpy of lattice formation, ∆H˚LF

Answer 4

Enthalpy change when one moles of a solid ionic compound is formed from its gaseous ions

Question 5

Standard enthalpy of formation, ∆H˚F

Answer 5

Enthalpy change hen one mole of a compound is formed from its constituent elements with all reactants and producers in their standard states

Question 6

Standard enthalpy of atomisation, ∆H˚at

Answer 6

Enthalpy change when one mole of gaseous atoms is formed from the element in its standard state

Question 7

Bond enthalpy

Answer 7

Heat energy required to break one mole of a given covalent bond in molecules in the gaseous state

Question 8

First ionisation energy, ∆H˚IE1

Answer 8

Energy needed to remove one mole of electrons from one mole of atoms in the gaseous state

Question 9

Second ionisation energy, ∆H˚IE2

Answer 9

Enthalpy change when one mole of gaseous 2+ ions are formed from one mole of gaseous 1+ ions

Question 10

First electron affinity, ∆H˚EA1

Answer 10

Enthalpy change when one mole of gaseous 1- ions are formed from one mole of gaseous atoms

Question 11

Second electron affinity, ∆H˚EA2

Answer 11

Enthalpy change when one mole of gaseous 2- ions are formed from one mole of gaseous 1- ions

Question 12

Enthalpy of solution, ∆H˚sol

Answer 12

Enthalpy change when one mole of an ionic substance dissolved in enough solvent to form an infinitely dilute solution

Question 13

Enthalpy of hydration, ∆H˚hyd

Answer 13

Enthalpy change when one mole of aqueous ions is formed from one mole of gaseous ions

Question 14

Entropy

Answer 14

Measure of disorder in a system

J mol-1 k-1