Thermodynamics (3) Flashcards
What does enthalpy measure ?
The heat content of a system
equation for enthalpy
deltaH= (products) - (reactants)
Which of the following is always true for an endothermic reaction ?
delta H is aleays positive in endothermic reactions
What is internal energy ?
energy that is gained though chemical systems that are translated into movement (e.g. traslation, vibration)
Where does the definition of enthalpy derive from ?
And what si the equation ?
- First Law of Thermodynamics
- H= U+pV
H= U+pV
what do the letters stand for ?
U= the energy to make it happen
pV= the energy needed to make room for it at constant pressure
what is the standard enthalpy of formation ?
it is the enthalpy change during the formation of 1 mole of the compound from its consituent elements
what is the standard enthalpy of combustion ?
it’s the enthalpy change during the complete combustion in oxygen of 1 mole
what is the standard enthalpy of fusion ?
it’s the enthalpy change during the formation of 1 mole of liquid through the melting of 1 mole of solid at a pressure of 1 bar
what is standard enthalpy of vapourisation
its’s the enthalpy change during the formation of 1 mole of gas through the boilling of 1 mole of liquid a pressure of 1 bar
What does Hess’ Law state?
It states that the enthalpy change from an initial to a final state is the same, regardless of the route taken
equation for Hess’ Law
products = reactants + reaction
equation for heats of formation data
products - reactants
the more disordered a substance……
the higher the S
