Thermodynamics

Question 1

Enthalpy change

Answer 1

Heat change of constant pressure

Question 2

Conditions for measuring enthalpy

Answer 2

298K

1 atmosphere

Question 3

Hess’ law

Answer 3

Overall enthalpy of reaction is independent of the route taken

Question 4

Enthalpy of formation algebra

Answer 4

🔼Hr* = Sum of 🔼Hf* products - sum of 🔼Hf* reactants.

Question 5

Standard molar enthalpy of formation

Answer 5

Enthalpy change when one mole of a compound is formed from its constituent elements under standard conditions, all reactants and products in their standard States.

Question 6

Standard molar enthalpy change of combustion

Answer 6

Enthalpy change when one mole of a substance is completely burnt in oxygen.

Question 7

Standard enthalpy of atomisation

Answer 7

Enthalpy change which accompanies the formation of one mole of gaseous atoms from the element in its standard state under standard conditions.

Question 8

First ionisation energy

Answer 8

Standard enthalpy change when one mole or gaseous atoms is converted into a mole of gaseous ions each with a single positive charge

Question 9

Second ionisation energy

Answer 9

Loss of a mole of electrons from a singly positively charged ions

Question 10

First electron affinity

Answer 10

enthalpy change when a mole of gaseous atoms is converted to a mole of gaseous negative ions

Question 11

Second electron affinity

Answer 11

Enthalpy change when a mole of electrons is added to a mole of gaseous ions each with a single negative charge to form ions each with two negative charges.

Question 12

Lattice enthalpy of formation

Answer 12

Standard enthalpy change when one mole of solid ionic compound is formed from its gaseous ions.

Question 13

Lattice enthalpy of dissociation

Answer 13

Standard enthalpy change when one mole of solid ionic compound dissociated into its gaseous ions.

Question 14

Enthalpy of solution

Answer 14

Standard enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecule or ions are far enough apart not to interact with each other.

Question 15

Enthalpy of hydration

Answer 15

Standard enthalpy change when water molecules surround one mole of gaseous ions.

Question 16

Mean bond enthalpy

Answer 16

Enthalpy change when one mole of gaseous molecules each breaks a covalent bond to form two free radicals, averaged over a range of compounds.

Question 17

Born Haber cycle

Answer 17

Thermochemical cycle that includes all the enthalpy changes involved in the formation of an ionic compound.