Answer: A new allotrope of oxygen, O4, has been reported.

Chapter 9, Problem 9.145

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A new allotrope of oxygen, O4, has been reported. The exact structure of O4 is unknown, but the simplest possible structure would be a four-member ring consisting of oxygen-oxygen single bonds. The report speculated that the O4 molecule might be useful as a fuel because it packs a lot of oxygen in a small space, so it might be even more energy-dense than the liquefied ordinary oxygen used in rocket fuel. (a) Draw a Lewis structure for O4 and write a balanced chemical equation for the reaction between ethane, C2H6(g), and O4(g) to give carbon dioxide and water vapor. (b) Estimate H for the reaction. (c) Write a chemical equation illustrating the standard enthalpy of formation of O4(g) and estimate Hf . (d) Assuming the oxygen allotropes are in excess, which will release more energy when reacted with ethane (or any other fuel): O2(g) or O4(g)? Explain using your answers to parts (a)(c)