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1) 3.00 g of p-aminophenol is reacted with 5.0 mL of acetic anhydride (density-

ID: 548681 • Letter: 1

Question

1) 3.00 g of p-aminophenol is reacted with 5.0 mL of acetic anhydride (density- 1.08 g/mL) to form acetaminophen and acetic acid as per the reaction below. What is the theoretical yield of acetaminophen? 2) When 3.044 g of salicylic acid is dissolved in acetic anhydride to make 9.000 ml solution, what is the molarity of the salicylic acid in the solution? Assume that none of the salicylic acid reacts upon dissolution. What is the solute and solvent in this solution? In terms of "like dissolves like" why does the solute dissolve? Would the solute dissolve in hexane? Explain. A student measured the melting point of their acetaminophen formed using the reaction in question 1, and found it to be 122-134 "C. The literature melting point of acetaminophen is 169 °C. Comment on the purity of their product based on their measured melting point. 3) 131

Explanation / Answer

Answer for Q-1

molar mass of p-aminophenol =109.1259g/mol

molar mass of acetic anhydride = 102.09 g/mol

moles of p-aminophenol = mass/molar mass

                                  = 3.0g/(109.1259g/mol)

                                  = 0.02749 mol

moles of acetic anhydride = mass/molar mass

                                         = 5.4g/(102.09g/mol) [calculated from given density]

                                         = 0.05289 mol

we know that for every mole of p-aminophenol and acetic acid one mole of acetaminophen is produced.

Since there are more moles of acetic anhydride than p-aminophenol.So, we can conclude that acetic anhydride is in excess and p-aminophenol is the limiting reagent.

Therefore no. of moles of p-aminophenol used = no. of moles acetaminophen produced

Finding the Theoretical Yield is,

Theoretical Yield = moles of acetamiophen x molar mass of acetaminophen

                         = 0.02749 mol x 151.163g/mol

                         = 4.155 g