[zerocoolaid]

I've been puzzled by the true meaning of enthalpy of reaction. Enthalpy of formation of compound is enthalpy generated to produce 1 mole of that compound.

So when you have a reaction

aA + bB -> cC + dD

Does the enthalpy of reaction really means change in enthalpy when "a" mole of A and "b" mole of B are consumed to produce "c" mole of C and "d" mole of D or does it really means enthalpy change until the equalibrium constant is reached?

[sdekivit]

what does the law of Hess mean ?