Answer : - 136.0 KJ/mol
Explanation : The complete question is attached below; assuming that the bond energies are given as per the question to find out the heat of formation of [tex] H_{2}O_{2}_{(g)} [/tex] we need to draw its lewis dot structure for this reaction;
[tex] H_{2}_{(g)} + O_{2}_{(g)} ----> H_{2}O_{2}_{(g)} [/tex]
[tex] H_{2} [/tex] will have H-H bond and [tex] O_{2} [/tex] will have O=O with 2 pairs of lone electrons on each of O atom.....These are the bonds which are broken
In [tex] H_{2}O_{2}_{(g)} [/tex] has H-O-O-H bonds; Here, O atom again has 2 pairs of lone pairs on each O atom; ....These are bonds which are made
ΔH°f = ∑ {ΔH(bonds broken) - ΔH (bonds made)}
ΔH°f = ∑ { (432 + 494) - [(459 X 2) +142] }
On solving, We get,
ΔH°f = -136.0 KJ/mol
Hence, the heat of formation for [tex] H_{2}O_{2}_{(g)} [/tex] will be -136.0 KJ/mol
