The balanced chemical equation for the preparation of 2,4-dinitrophenol from phenol and nitric acid is:C6H5OH + 2 HNO3 C6H3 NO2 2OH + 2 H2OTo calculate the mass of nitric acid required to produce 25 grams of 2,4-dinitrophenol with a 90% yield, we first need to determine the theoretical yield and then the actual yield.1. Calculate the molar mass of 2,4-dinitrophenol C6H3 NO2 2OH :Molar mass = 6 12.01 + 3 1.01 + 2 14.01 + 2 16.00 + 1.01 + 16.00 Molar mass = 184.11 g/mol2. Calculate the moles of 2,4-dinitrophenol needed for 25 grams:moles = mass / molar massmoles = 25 g / 184.11 g/molmoles = 0.1358 mol3. Calculate the theoretical yield:Theoretical yield = moles of 2,4-dinitrophenol / moles of nitric acidSince the balanced equation shows a 1:2 ratio between phenol and nitric acid, we need twice the moles of nitric acid:moles of nitric acid = 0.1358 mol 2moles of nitric acid = 0.2716 mol4. Calculate the actual yield 90% :Actual yield = theoretical yield 0.90Actual yield = 0.2716 mol 0.90Actual yield = 0.2444 mol5. Calculate the mass of nitric acid required HNO3 molar mass = 63.01 g/mol :mass = moles molar massmass = 0.2444 mol 63.01 g/molmass = 15.39 gTherefore, 15.39 grams of nitric acid are required to produce 25 grams of 2,4-dinitrophenol with a 90% yield.