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Question 5 (14 + 6 + 6 + 12 + 7 + 9 = 54 marks) = = Ibuprofen (C13H1802) is a weakly acidic molecule with a pka = 4.9. It has an estimated solubility of 0.021 mg/ml at 20 °C and a log P = 3.83 (M(C) = 12.01 g/mol; M(O) = 16.00 g/mol). = = au OH Ibuprofen (a) Determine the pH of a 18 mg/L aqueous solution of ibuprofen in pure water. (b) If 18 mg/L aqueous solution of ibuprofen was prepared using 0.5 M NaCl solution. Would you expect the pH of the solution to be different? If so, how? Provide reasons to support your answer. (c) What percentage of ibuprofen will be ionised: (i) in a pH 5.0 solution and (ii) a pH 7.8 solution. (d) Determine the total solubility of ibuprofen at a pH of 7.8. (e) The solubility of ibuprofen increases with increasing solution pH. Briefly explain why this occurs. The aqueous solubility of ibuprofen is very low (0.021 mg/mL at 20 °C). Describe three ways in which you could try to formulate an ibuprofen liquid dosage form with a higher concentration of ibuprofen.