The boiling point of pure benzene (C₆H₆) is 80.10 ° C. A solution of 7.39 g of a solid dissolved in 85.0 g of benzene boils at 82.49 ° C. If k_b for benzene is 2.53 ° C/molal, the molar mass of the solid is:

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The boiling point elevation formula is ΔTb = i * Kb * m, where ΔTb is the change in boiling point, i is the van't Hoff factor (which is 1 for non-electrolytes), Kb is the ebullioscopic constant of the solvent, and m is the molality of the solution. Given ΔTb = 82.49 °C - 80.10 °C = 2.39 °C, Kb = 2.53 °C/molal, and the mass of solute and solvent, we can solve for the molar mass of the solid. First, calculate the molality (m) = moles of solute/kg of solvent. Rearranging the formula to solve for the molar mass of the solute gives us the molar mass = (mass of solute in grams) / [(ΔTb / (Kb * mass of solvent in kg))]. Plugging in the given values, we find the molar mass to be approximately 92.0 g/mol.

The Boiling Point of Pure Benzene (C6H6) Is 80

The Boiling Point of Pure Benzene (C₆H₆) Is 80