Definitions - Enthalpy Flashcards
Activation energy
The minimum energy required for a reaction to occur
Bond enthalpy
The enthalpy change that takes place when 1 mole of a specified bond is broken into its atoms in the gas phase
Endothermic
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants (ΔH is positive)
Enthalpy (H)
The heat content of a chemical measured at constant pressure
Exothermic
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants (ΔH is negative)
Hess’ Law
The enthalpy change of a reaction is independent of the route, it only depends on the initial and final stages
Mean bond enthalpy
The enthalpy change that takes place when 1 mole of a specified bond is broken into its atoms in the gas phase averaged over many compounds containing that bond
Specific heat capacity (c)
The energy in Joules required to raise the temperature of 1g of a substance by 1 K
Standard conditions
Pressure of 100kPa, temperature of 298K (25oC), and aqueous solutions of concentration 1.00 mol dm-3
The standard enthalpy change of combustion ΔcHӨ
The enthalpy change when 1 mole of a substance reacts completely with oxygen measured under standard conditions
The standard enthalpy change of formation ΔfHӨ
The enthalpy change when 1 mole of a substance is formed from its elements measured under standard conditions
The standard enthalpy change of reaction ΔrHӨ
The enthalpy change for a chemical reaction for the quantities in the chemical equation measured under standard conditions
The standard enthalpy change of neutralisation ΔneutHӨ
The enthalpy change for a chemical reaction between an aqueous acid and an aqueous alkali to produce 1 mole of water measured under standard conditions
