Estimate the bond energy for the oxygen-oxygen bond in ozone, O3?

Question

Oxygen atoms can combine with ozone to form oxygen.
O3(g) + O(g) -> 2 O2(g)
(delta)H°rxn = -394 kJ

(a) Using (delta)H°rxn and the bond energy data in Table 1, estimate the bond energy for the oxygen-oxygen bond in ozone, O3. _____kJ/mol

(b) How does your estimate compare with the energies of an O-O single bond and an O=O double bond? Explain

(c) Does the oxygen-oxygen bond energy in ozone correlate with its bond order? (yes/no)

Table 1 : http://www.webassign.net/kt/9-10tab.gif

Answer 1

You need to find the total energy of formation from the atoms

3 O = O3 (1)

And divide by two because there are two bonds.

To get the energy of (1), combine the two equations

4 O = 2 O2 (DeltaH near enough 2 x the negative of the O=O bond energy)

2 O2 = O3 + O (DeltaH + 394 kJ)

These add up to (1)

Advanced note: I have ignored the difference between DeltaH and DeltaE, because volume change effects in a case like this are much smaller than bond effects.

(b) and (c): write down the Lewis structure for O3. Remember that there are two canonical forms which contribute equally to the structure. This will tell you what the valence bond order is. You can compare that with the energies of O-O and O=O (from tables). It should be, very roughly, about halfway in between.

Answer 2

breaking the O-O bond to make O2 from O3 releases 391.9kJ ability. if we seem at it interior the choice course, including and O to O2 to make O3 demands an enter of 391.9kJ ability. this could incorporate breaking between the bonds in O=O, making it accessible for yet another O to bond. the breaking of an O=O bond and the formation of O=O=O bonds. the 391.9kJ contains the breaking of the O=O bond in 2 moles of O2, so 2 bonds could desire to be broken freeing ability, and the formation of O=O=O requiring ability. deltaH = 391.9kJ = (O=O=O) - 2(O=O)