energetics definitions

Question 1

Standard enthalpy change of combustion (ΔcH°)

Answer 1

The enthalpy change when one mole of a fuel is combusted completely in oxygen under standard conditions (1atm and 298K).

Question 2

Standard enthalpy change of formation (ΔfH°)

Answer 2

The enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions.
(for reversible reaction it is assumed that the reaction goes completely to the right hand side)

Question 3

Standard enthalpy change of neutralisation (ΔnH°)

Answer 3

The enthalpy change when an acid and an alkali react together under standard conditions to give one mole of water.

Question 4

Standard enthalpy change for a reaction (ΔrH°)

Answer 4

The enthalpy change when substances react under standard conditions in quantities given by the equation for the reaction.

Question 5

Standard enthalpy change of atomisation (ΔaH°)

Answer 5

The enthalpy change when one mole of gaseous atoms is formed from the element in its standard state.

Question 6

ionisation enthalpy (ΔieH°)

Answer 6

The energy required to remove an electron from one mole of gaseous atoms to form one mole of gaseous 1+ ions