Enthalpies

Question 1

Define enthalpy change of formation

Answer 1

Enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions

Question 2

Define enthalpy change of atomisation of an element

Answer 2

Enthalpy change when one mole of gaseous atoms is formed from an element in it’s standard state

Question 3

Define enthalpy change of hydration

Answer 3

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

Question 4

Define enthalpy change of solution

Answer 4

Enthalpy change when one mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution

Question 5

Define enthalpy change of atomisation of a compound

Answer 5

Enthalpy change when one mole of a compound in its standard state is converted to gaseous atoms

Question 6

Define bond dissociation enthalpy

Answer 6

The enthalpy change when all the bonds of the same type in one mole of gaseous molecules are broken

Question 7

Define first ionisation energy

Answer 7

Enthalpy change when one mole of gaseous 1+ ions is formed from one mole of gaseous atoms

Question 8

Define second ionisation energy

Answer 8

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

Question 9

Define first electron affinity

Answer 9

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

Question 10

Define second electron affinity

Answer 10

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

Question 11

Is a reaction exothermic or endothermic for negative enthalpies

Answer 11

Exothermic as heat energy is given out

Question 12

Is a reaction exothermic or endothermic for positive enthalpies

Answer 12

Endothermic as heat energy is absorbed

Question 13

Do soluble substances tend to have endo or exothermic enthalpies

Answer 13

Exothermic enthalpies