Topic 8 key definitions

Question 1

Standard enthalpy change of reaction.

Answer 1

The enthalpy change measured at 100kPa and usually 298K when one mole of substance reacts.

Question 2

Standard enthalpy change of combustion.

Answer 2

The enthalpy change measured at 298K and 100KPa when one mole of substance is completely burned in oxygen.

Question 3

Standard enthalpy change of neutralisation.

Answer 3

The enthalpy change at 100Kpa and 298K when one mole of water is produced by the neutralisation of an acid with an alkali.

Question 4

Standard enthalpy change of formation.

Answer 4

The enthalpy measured at 100kPa and usually 298K when one mole of substance is formed from elements in their standard states.

Question 5

Hess’s law?

Answer 5

The enthalpy change of a reaction is independent of the route taken in converting the reactants into products, providing conditions stay constant.