A1: Enthalpy Flashcards
Define average bond enthalpy
Energy required to break one mole of a specific bond in a gaseous molecule
Why is exothermic ΔH negative and endothermic positive
Exothermic: energy released when making bonds > energy required to break bonds
Endothermic: energy required to break bonds>energy released to make bonds
What are the standard conditions
100kPa, 298K, 1moldm^-3
Define standard state
The physical state of a substance under standard conditions
Enthalpy change of a reaction (ΔrH)
The enthalpy change that accompanies a reaction with a stated equation
Define enthalpy change of formation (ΔfH)
The enthalpy change that takes place when one mole of a compound is formed from its elements
Define enthalpy change of combustion (ΔcH)
The enthalpy change that takes place when one mole of a substance undergoes complete combustion
Define enthalpy change of neutralisation (ΔneutH)
The enthalpy change that accompanies the reaction of an acid with a base to form one mole of H2O(l)
Define enthalpy (H)
A measure of the heat energy in a chemical system
Enthalpy change (ΔH)
H(products)-H(reactants)
Exothermic change (-ΔH)
Chemical system releases heat energy to the surroundings
Endothermic change (+ΔH)
Chemical system takes in heat from surroundings
