A 12-year-old child has bacterial pharyngitis and is to receive an oral antibiotic

A 12-year-old child has bacterial pharyngitis and is to receive an oral antibiotic. She complains of a sore throat and pain on swallowing. The tympanic membranes are slightly reddened bilaterally, but she does not complain of earache. Blood pressure is 105/70 mm Hg, heart rate 100/mm, temperature 37.8 C (100.1 F). Ampicillin is a weak organic acid with a pKa of 2.5 . What percentage of a given dose will be in the lipid-soluble form in the duodenum at a pH of 4.5 ? a) About 1% b) About 10% c) About 50% d) About 90% e) About