Energetics Flashcards
Definition of enthalpy change
A measurement of heat energy change under a constant pressure
Units - KJmol-1
What are making and breaking bonds?
Breaking - endothermic (+)
Making - exothermic (-)
Reactant minus product
What is the enthalpy of formation definition
The enthalpy change when one mole of a compound is formed from its elements under standard conditions, with both reactants and products being in their standard states
Example equation of formation
NaOH
Na(s) + 1/2O2(g) + 1/2H2(g) —> NaOH(aq)
What is the enthalpy of combustion definition
The enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions, with both the reactants and products in their standard states
Example equation of combustion
C3H8
C3H8 + 5O2 —> 3CO2 + 4H20
State Hess’s Law
The enthalpy change for a chemical reaction is independent of the route taken
Equation for calculating enthalpy change
Q = mcΔt
What unit is enthalpy change?
KJmol-1
