4.4-7 The rest of enthalpy Flashcards
1
Q
What does Hess’s law state?
A
that the enthalpy change for a chemical reaction is the same, whatever route is taken from reactants to products
2
Q
Why are calculations from mean bond enthalpies often different
from those calculated from Hess’ Law (theoretical values)?
A
Bond enthalpies are a mean average taken over a range of compounds
3
Q
How is enthalpy change (ΔH) calculated from enthalpy change of
formation data? (ΔHf )
A
ΔH = ΣΔHf (products) - ΔHf (reactants)
4
Q
How is enthalpy change (ΔH) calculated from enthalpy change of
combustion data? (ΔHc )
A
ΔH = ΣΔHc (reactants) - ΔHc (products)
5
Q
How is enthalpy change (ΔH) calculated from bond enthalpy data?
A
ΔH = Σ bond enthalpy (reactants) - Σ bond enthalpy (products)
