Chapter 8

Draw resonance structures for the \(\mathrm{SO}_{2}\) molecule, and determine the formal charges on the \(\mathrm{S}\) and \(\mathrm{O}\) atoms. Are the \(\mathrm{S}-\mathrm{O}\) bonds polar, and is the molecule as a whole polar? If so, what is the direction of the net dipole in \(\mathrm{SO}_{2}\) ? Is your prediction confirmed by the electrostatic potential surface? Explain briefly. (IMAGE NOT COPY)

What are the orders of the \(\mathrm{N}-\mathrm{O}\) bonds in \(\mathrm{NO}_{2}^{-}\) and \(\mathrm{NO}_{2}^{+} ?\) The nitrogen-oxygen bond length in one of these ions is \(110 \mathrm{pm}\) and \(124 \mathrm{pm}\) in the other. Which bond length corresponds to which ion? Explain briefly.

Which has the greater O-N-O bond angle, \(\mathrm{NO}_{2}^{-}\) or \(\mathrm{NO}_{2}^{+} ?\) Explain briefly.

Compare the \(\mathrm{F}-\mathrm{Cl}-\mathrm{F}\) angles in \(\mathrm{ClF}_{2}^{+}\) and \(\mathrm{ClF}_{2}^{-} .\) Using Lewis structures, determine the approximate bond angle in each ion. Decide which ion has the greater bond angle, and explain your reasoning.

Draw an electron dot structure for the cyanide ion, CN'. In aqueous solution, this ion interacts with \(\mathrm{H}^{+}\) to form the acid. Should the acid formula be written as HCN or CNH?

Draw the electron dot structure for the sulfite ion, \(\mathrm{SO}_{3}^{2-} .\) In aqueous solution, the ion interacts with \(\mathrm{H}^{+}\) Predict whether a \(\mathrm{H}^{+}\) ion will attach to the \(\mathrm{S}\) atom or the \(\mathrm{O}\) atom of \(\mathrm{SO}_{3}^{2-}\).

The cyanate ion, \(\mathrm{OCN}^{-}\), has the least electronegative atom, \(\mathrm{C}\), in the center. The very unstable fulminate ion, CNO \(^{-}\), has the same molecular formula, but the \(\mathrm{N}\) atom is in the center. (a) Draw the three possible resonance structures of \(\mathrm{CNO}^{-}\). (b) On the basis of formal charges, decide on the resonance structure with the most reasonable distribution of charge. (c) Mercury fulminate is so unstable it is used in blasting caps for dynamite. Can you offer an explanation for this instability? (Hint: Are the formal charges in any resonance structure reasonable in view of the relative electronegativities of the atoms?)

Given that the spatial requirement of a lone pair is greater than that of a bond pair, explain why (a) \(\mathrm{XeF}_{2}\) has a linear molecular structure and not a bent one. (b) CIF \(_{3}\) has a T-shaped structure and not a trigonalplanar one.

You are doing an experiment in the laboratory and want to prepare a solution in a polar solvent. Which solvent would you choose, methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right)\) or toluene \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{3}\right) ?\) Explain your choice. (IMAGE NOT COPY)

Methylacetamide, \(\mathrm{CH}_{3} \mathrm{CONHCH}_{3},\) is a small molecule with an amide link (CO-NH), the group that binds one amino acid to another in proteins. (a) Is this molecule polar? (b) Where do you expect the positive and negative charges to lie in this molecule? Does the electrostatic potential surface confirm your predictions? (IMAGE NOT COPY)

A paper published in the research journal Science in 2007 (S. Vallina and R. Simo, Science, Vol. \(315,\) p. \(506,\) January 26,2007 ) reported studies of dimethylsulfide (DMS), an important greenhouse gas that is released by marine phytoplankton. This gas "represents the largest natural source of atmospheric sulfur and a major precursor of hygroscopic (i.e., cloud-forming) particles in clean air over the remote oceans, thereby acting to reduce the amount of solar radiation that crosses the atmosphere and is absorbed by the ocean." (a) Sketch the Lewis structure of dimethylsulfide, \(\mathrm{CH}_{3} \mathrm{SCH}_{3},\) and list the bond angles in the molecule. (b) Use electronegativities to decide where the positive and negative charges lie in the molecule. Is the molecule polar? (c) The mean seawater concentration of DMS in the ocean in the region between \(15^{\circ}\) north latitude and \(15^{\circ}\) south latitude is \(2.7 \mathrm{nM}\) (nanomolar). How many molecules of DMS are present in \(1.0 \mathrm{m}^{3}\) of seawater?

Acrylamide, \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CHC}(=\mathrm{O}) \mathrm{NH}_{2},\) is a known neuro- toxin and possible carcinogen. It was a shock to all consumers of potato chips and french fries a few years ago when it was found to occur in those products. (a) Sketch the molecular structure of acrylamide and identify all bond angles. (b) Indicate which carbon-carbon bond is the stronger of the two. (c) Is the molecule polar or nonpolar? (d) The amount of acrylamide found in potato chips is \(1.7 \mathrm{mg} / \mathrm{kg} .\) If a serving of potato chips is \(28 \mathrm{g},\) how many moles of acrylamide are you consuming?