Enthalpy Definitions

Question 1

What is an exothermic reaction?

Answer 1

Exothermic reactions have a negative deltaH value, heat energy is given out

Question 2

What is an endothermic reaction?

Answer 2

Endothermic reactions have a positive deltaH value, heat energy is absorbed

Question 3

Define enthalpy change of formation

Answer 3

Enthalpy change of formation is the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions

Question 4

Define bond dissociation enthalpy

Answer 4

Bond dissociation enthalpy is the enthalpy change when all the bonds of the same type in 1 mole of gaseous molecules are broken

Question 5

Define enthalpy change of atomisation of an element

Answer 5

Enthalpy change of atomisation of an element is the enthalpy change when 1 mole of gaseous atoms is formed from its element in its standard state

Question 6

Define enthalpy change of atomisation of a compound

Answer 6

Enthalpy change of atomisation of a compound is the enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms

Question 7

Define first electron affinity

Answer 7

The first electron affinity is the enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms

Question 8

Define second electron affinity

Answer 8

The second electron affinity is the enthalpy change when 1 mole of gaseous 2- ions is formed from 1 mole of gaseous 1- ions

Question 9

Define enthalpy change of hydration

Answer 9

Enthalpy change of hydration is the enthalpy change when 1 mole of aqueous ions is formed from 1 mole of gaseous ions

Question 10

Define enthalpy change of solution

Answer 10

Enthalpy change of solution is the enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution