Is SO2 a liquid, a solid, or a gas at room temperature?

Question

Henry Antrim · Accepted Answer

#"SO"_2# is a gas at room temperature.

a gas. You can start simply by thinking about #SO_2# having covalent bonds and a simple molecular structure like #CO_2#. To go into a little more depth, we need to think about what type(s) of intermolecular forces #SO_2# has. Like all simple molecules it will have the weakest intermolecular forces, Van der Waals. It is also a polar molecule, because it has a bend shape as a result of having two (double) binding pairs and a lone pair on the central S atom. The S atom is less electronegative that O, so the S-O bonds are polar and not symmetrically opposed, so the dipoles don't cancel each other out and we have permanent dipole-dipole intermolecular forces which are stronger than Van der Waals, so we'd expect a higher melting and boiling point than #CO_2#. In summary, we expect a low melting and boiling point for sulfur dioxide, but not as low as for carbon dioxide; the actual melting point is -72 degrees Celsius, compared to a melting point of -78.5 degrees Celsius for carbon dioxide, and the boiling point is -10 degrees Celsius, compared to -56.6 degrees Celsius for carbon dioxide. These figures show that both gases are at room temperature. This is because sulfur dioxide cannot form hydrogen bonds, the strongest intermolecular force.

Jose Ayala · Answer

undefined At room temperature, SO2 is a gas.