Lets number the reaction as 1, 2, 3 from top to bottom
required reaction should be written in terms of other
reaction
This is Hess Law
required reaction can be written as:
reaction 3 = +1 * (reaction 1) -1 * (reaction 2)
So, ΔHo rxn for required reaction will be:
ΔHo rxn = +1 * ΔHo rxn(reaction 1) -1 * ΔHo rxn(reaction 2)
= +1 * (-795.8) -1 * (-224.3)
= -571.5 KJ
Answer: -571.5 KJ
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