3.45. Draw an important resonance structure for each of the following molecules. Each part represents one of the common situations described in Sec. 3.3. Depict the resonance hybrid as a single structure with dashed lines and partial charges. (a) (b) [H2CCH3 (c) (d) 3.46. Given the following structures of resonance hybrids, provide the three contributing resonance structures for (a) and (b), and four structures for (c). 3.51 (a) Write the chemical equation for acid dissociation of trimethylammonium ion with water as a base. Trimethylammonium ion (b) Write the expression for the dissociation constant Ka in terms of the equilibrium concentration of all species. 3.55. Phenylacetic acid (PhCH2CO2H),pKa=4.31, was dissolved in a pH=4.5 buffer at an initial concentration of 104M. What is the concertation of phenylacetic acids and its conjugate base in the buffer solution