Chapter 2, Problem 32P

Volcanoes and deep sea hydrothermal vents are both associated with sulfur-rich environments. Mount Etna is classed as a continuously degassing volcano and emissions of ${\text{SO}}_2$ and ${\text{H}}_{\text{2}}\text{S}$ are around $1.5\text{Tg}{\text{y}}^{\text{-1}}$ and $100\text{Gg}{\text{y}}^{\text{-1}}$, respectively ( $\text{Tg}\text{=}{\text{10}}^{\text{12}}\text{g}$; $\text{Gg}\text{=}{\text{10}}^{\text{9}}\text{g}$). (a) Draw Lewis structure for ${\text{H}}_{\text{2}}\text{S}$ and ${\text{SO}}_{\text{2}}$, ensuring that the octet rule is obeyed by S and O atoms. Your answer must be consistent with the fact that in ${\text{SO}}_{\text{2}}$, the two sulfur-oxygen bonds are the same length. (b) Are ${\text{H}}_{\text{2}}\text{S}$ and ${\text{SO}}_{\text{2}}$ polar or non-polar molecules? If polar, draw a diagram to show the direction of the molecular dipole moment. (c) In the troposphere, ${\text{SO}}_{\text{2}}$ reacts with ${\text{HO}}^{·}$ radicals. Construct an MO diagram for ${\text{HO}}^{·}$ from H and O atoms, and deduce what you can about the bonding in ${\text{HO}}^{·}$.