# Why is the energy needed to transform PbO+CO into Pb+O2+C equal to the sum of breaking down PbO and CO? [closed]

Since PbO to Pb+(1/2)O2 releases 217.3kJ and CO to C+(1/2)O2 releases 110.5kJ, what I think is that PbO+CO to Pb+(1/2)O2+C+(1/2)O2 releases 327.8kJ. Now, the book says PbO+CO to Pb+C+O2 releases 327.8kJ.

My question is, why does is there no energy involved making Pb+(1/2)O2+C+(1/2)O2 into Pb+C+O2? Wouldn't there be some energy released joining the two halfs of oxygen?

• why did the O become (1/2)O2? – 12345bird May 13 '20 at 10:18
• It's like how half a dozen eggs + half a dozen eggs = one dozen eggs. It's not a dozen of half-eggs (that would be a tragedy!). – orthocresol May 13 '20 at 18:03
• oh ok, thanks! thats a funny analogy! – 12345bird May 14 '20 at 16:51

There are no two halfs of oxygen. The half denotes that there is $$\frac{1}{2}$$ a mole of oxygen produced for every mole of $$\ce{PbO}$$ (or $$\ce{CO}$$) reacting. So there is no such "joining of oxygen halves" going on.