Oxygen and Ozone

[serge]

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Hey everyone

Most textbooks explain that ozone is blue (atleast when it condenses)
and oxygen is clear, and that ozone has a distinct odour...
they dont really back up these descriptions with how
the two different structures cause these differences?

any ideas? (no need to explain reactivity or BP)

cheers

[serge]

has anyone been taught this?

[Casmira]

• Compare the properties of gaseous forms of Oxygen allotrope O2 and O3
Account for them on the basis of molecular structure and bonding


Oxygen | Ozone
Colorless | Colourless
Slightly soluble in water | Very soluble in water
Odourless | Pugnent smell
BP 184°C | BP 112°C

Oxygen is non polar and doesn’t form strong intermolecular bonds with water (polar) and is only slightly soluble. The BP of Oxygen is lower due to lower atomic mass of oxygen and less energy is needed to break these bonds.

Ozone is a bent, polar structure and is more soluble in water, ozone has a higher BP due to the polar nature and ozone will increase attraction between molecules and thus increase the BP.

Oxygen is very stable covalent bond and 493kJ mol-1 of energy is needed to break bonds of 1 mole of O2 molecules, Ozone only needs 1/3 that energy to break its bond, and ozone forms a free radical and Oxygen.


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From wikipedia:
"Ozone is a colorless gas at standard temperature and pressure. It forms a dark blue liquid below -112 °C and a dark blue solid below -193 °C. Ozone is a powerful oxidizing agent. It is also unstable, decaying to ordinary oxygen through the reaction:"

"Liquid O2 and solid O2 have a light blue color and both are highly paramagnetic. Liquid O2 is usually obtained by the fractional distillation of liquid air. [Oxygen gas is colourless]"

[Lachycharts]

I know this thread is old, but for future reference since I also riddled over this question but found my answers through my understanding of physics and also various sites. Basically I have written this in my assessment:

Different molecules/atoms absorb and reflect light at different frequencies (this is what determines the colour of a substance) due to the energy states of the electrons. Due to the differences in bonding in ozone and oxygen, ozone has different electron states to O₂ and absorbs all but blue light and oxygen absorbs and reflects light in which the human eye cannot see, hence the reason why it is observed to be colourless.