enthalpy changes: definitions

Question 1

activation energy

Answer 1

the minimum energy required for a chemical reaction to take place by breaking bonds in the reactiants

Question 2

enthalpy change ΔH

Answer 2

the amount of (thermal) energy transferred during a chemical reaction at constant pressure

Question 3

standard enthalpy change of a reaction ΔᵣHᶿ

Answer 3

the enthalpy change for a given reaction in the molar quantities shown in the equation

Question 4

standard enthalpy of combustion ΔcHᶿ

Answer 4

the enthalpy change when one mole of a substance undergoes complete combustion under standard conditions

Question 5

standard enthalpy of formation ΔfHᶿ

Answer 5

the enthaly change when one mole of a substance is formed from its elements under standard conditions

Question 6

standard enthalpy change of neutralisation ΔneutHᶿ

Answer 6

the enthalpy change when one mole of H₂O is formed from the reaction of H⁺ and OH⁻ under standard conditions

Question 7

specific heat capacity

Answer 7

The amount of thermal energy required to raise the temperature of 1kg of a substance by 1°C (1K)
– check units

Question 8

average bond enthalpy

Answer 8

the enthalpy change for the breaking of one mole of bonds in gaseous molecules

Question 9

Hess’ Law

Answer 9

the enthalpy change for a given reaction is independant of the route taken