3.2.1 Enthalpy Changes

Question 1

Standard enthalpy of combustion

Answer 1

Enthalpy change when one mole of a substance
Is completely burned in excess oxygen
Under standard conditions of 298K and 100kPa

Question 2

Standard enthalpy of formation

Answer 2

The enthalpy change when one mole of a substance
Is formed from its elements in their standard states
Under standard conditions of 208K and 100kPa

Question 3

Standard enthalpy change of neutralisation

Answer 3

The enthalpy change of one mole of H2O
Is formed from the reaction of an acid with a base
Under standard conditions of 298K and 100kPa

Question 4

Why are bond enthalpies described as average enthalpies.

Answer 4

Each individual bond will be in a different environment and therefore have a different strength