Thermodynamics + energetics definitions

Question 1

What is enthalpy

Answer 1

Heat energy change at constant pressure

Question 2

Standard molar enthalpy of formation

Answer 2

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

Question 3

Standard molar enthalpy of combustion

Answer 3

Enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions with all reactants and products in their standard states

Question 4

Standard enthalpy of atomisation

Answer 4

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

Question 5

First ionisation energy

Answer 5

(always positive - endothermic)
Enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single positive charge

Question 6

Second ionisation energy

Answer 6

(always positive)
Enthalpy change when one mole of electrons are lost from a mole of single positively charged ions

Question 7

First electron affinity

Answer 7

(always negative)
Standard enthalpy change when one mole of gaseous atoms is converted to one mole of gaseous ions each with a single negative charge

Question 8

Second electron affinity

Answer 8

(always positive)
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 9

Lattice enthalpy of formation

Answer 9

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

Question 10

Lattice enthalpy of dissociation

Answer 10

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

Question 11

Enthalpy of hydration

Answer 11

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

Question 12

Enthalpy of solution

Answer 12

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

Question 13

Bond enthalpy of dissociation

Answer 13

Enthalpy change when one mole of covalent bond is broken into 2 gaseous atoms

Question 14

Mean bond enthalpy

Answer 14

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

Question 15

Standard enthalpy change of reaction

Answer 15

Enthalpy change when a reaction occurs in the molar quantities shown in the chemical equation under standard conditions with all reactants and products in their standard states