DF2: Enthalpy cycles + Hess' Law Flashcards
What is Hess’s Law?
If the starting and ending points are the same, so is the total enthalpy change of a reaction, no matter what route is taken.
What is the formula for finding the enthalpy change of reaction (H) from enthalpy changes of combustion?
Clockwise enthalpy changes = Counter-clockwise enthalpy change
What is the formula for finding the enthalpy change of reaction from enthalpy changes of formation?
Enthalpy change of reaction = sum of enthalpy changes of formation of products - sum of enthalpy changes of formation of reactants
Which ways do the arrows point in an enthalpy cycle for combustion?
Towards the products (Oxides)
Which ways do the arrows point in an enthalpy cycle for formation?
Away from elements in their standard states
Why is the amount of oxygen used in combustion not critical?
It is normally used in excess to ensure complete combustion
Why are the enthalpy changes for elements always 0?
They have already been formed and do not change their amount so enthalpy change is 0
