Problem 104
Most organic acids can be represented as \(\mathrm{RCOOH}\) where \(\mathrm{COOH}\) is the carboxyl group and \(\mathrm{R}\) is the rest of the molecule. [For example, \(\mathrm{R}\) is \(\mathrm{CH}_{3}\) in acetic acid \(\left.\left(\mathrm{CH}_{3} \mathrm{COOH}\right) .\right]\) (a) Draw a Lewis structure for the carboxyl group. (b) Upon ionization, the carboxyl group is converted to the carboxylate group \(\left(\mathrm{COO}^{-}\right)\). Draw resonance structures for the carboxylate group.
Problem 105
Which of the following species are isoelectronic: \(\mathrm{NH}_{4}^{+}, \mathrm{C}_{6} \mathrm{H}_{6}, \mathrm{CO}, \mathrm{CH}_{4}, \mathrm{~N}_{2}, \mathrm{~B}_{3} \mathrm{~N}_{3} \mathrm{H}_{6} ?\)
Problem 106
Draw three resonance structures for the hydrogen sulfite ion \(\left(\mathrm{HSO}_{3}^{-}\right)-\) one that obeys the octet rule for the central atom, and two that expand the octet of the central atom. Calculate the formal charges on all atoms in each structure and determine which, if any, of the resonance structures has formal charges that are inconsistent with the elements' electronegativities.
Problem 107
Draw two resonance structures for each species \(-\) one that obeys the octet rule, and one in which the formal charge on the central atom is zero: \(\mathrm{PO}_{4}^{3-}, \mathrm{HClO}_{3}\), \(\mathrm{SO}_{3}, \mathrm{SO}_{2}\)
Problem 108
The following species have been detected in interstellar space: (a) CH, (b) OH, (c) \(\mathrm{C}_{2},(\mathrm{~d}) \mathrm{HNC}\) (e) HCO. Draw Lewis structures for these species.
Problem 109
The amide ion \(\left(\mathrm{NH}_{2}^{-}\right)\) is a Brønsted base. Use Lewis structures to represent the reaction between the amide ion and water.
Problem 110
Draw Lewis structures for the following organic molecules: (a) tetrafluoroethylene \(\left(\mathrm{C}_{2} \mathrm{~F}_{4}\right),(\mathrm{b})\) propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right),(\mathrm{c})\) butadiene \(\left(\mathrm{CH}_{2} \mathrm{CHCHCH}_{2}\right),(\mathrm{d})\) propyne \(\left(\mathrm{CH}_{3} \mathrm{CCH}\right),\) (e) benzoic acid \(\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\right)\). (To draw \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH},\) replace an \(\mathrm{H}\) atom in benzene with a COOH group.)
Problem 111
The triiodide ion \(\left(\mathrm{I}_{3}^{-}\right)\) in which the I atoms are arranged in a straight line is stable, but the corresponding \(\mathrm{F}_{3}^{-}\) ion does not exist. Explain.
Problem 113
In 1999, an unusual cation containing only nitrogen \(\left(\mathrm{N}_{5}^{+}\right)\) was prepared. Draw three resonance structures of the ion, showing formal charges.
Problem 114
Write the formulas of the binary hydrides for the second-period elements from \(\mathrm{Li}\) to \(\mathrm{F}\). Identify the bonding in each as covalent, polar covalent, or ionic.
