To calculate the melting point of the solution, we need to first determine the molality of the solution and then use the freezing point depression equation.1. Calculate the moles of benzoic acid solute and naphthalene solvent :Molar mass of benzoic acid C6H5COOH = 12 6 + 1 5 + 12 + 16 2 = 72 + 5 + 12 + 32 = 121 g/molMoles of benzoic acid = mass / molar mass = 20 g / 121 g/mol = 0.1653 molMolar mass of naphthalene C10H8 = 12 10 + 1 8 = 120 + 8 = 128 g/molMoles of naphthalene = mass / molar mass = 80 g / 128 g/mol = 0.625 mol2. Calculate the molality of the solution:Molality m = moles of solute / mass of solvent in kg Molality m = 0.1653 mol / 80 g / 1000 = 0.1653 mol / 0.080 kg = 2.066 mol/kg3. Use the freezing point depression equation:Tf = Kf * mTf = 6.8 C/m * 2.066 mol/kg = 14.049 C4. Calculate the new melting point of the solution:New melting point = pure naphthalene melting point - TfNew melting point = 80.2 C - 14.049 C = 66.151 CThe melting point of the solution containing 20 g of benzoic acid and 80 g of naphthalene is approximately 66.151 C.