Hey, I'm really struggling with Hess's cycle especially of a reaction.
I've been doing this question for ages and i still can't get my head around it could anyone help ?
Question
Lead forms several solid oxides the most common ones are PbO , PbO2 and Pb3O4.
Part 1 said write an equation for the formation of PbO
then Part 2 said, 3PbO+1/2O2= Pb3O4
enthalpies of formation are:
PbO=-219
Pb3O4=-735
I worked out the standard enthalpy change of the reaction and it came to 78kJmol-1
but this is is the part I'm confused by ...
when Pb3O4 is heated it decomposes to PbO and PbO2
enthalpy change of the reaction is 20kJmol-1
so now i need to find the enthalpy change of formation of PbO2 from this data