Hexachlorophene is used as a disinfectant in germicidal soaps. What mass of hexachlorophene (406.9 g/mol) must be added to 125 g of chloroform to give a solution with a boiling point of 62.60°C? (For chloroform, K_b = 3.63°C/m; boiling point of pure chloroform = 61.20°C) A) 19.6 g B) 17.2 g C) 40.7 g D) 50.9 g E) 157 g

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Quizplus · Accepted Answer

The boiling point elevation formula is $\Delta T_b = iK_b m$, where $\Delta T_b$ is the change in boiling point, $K_b$ is the ebullioscopic constant, and $m$ is the molality of the solution. Given that the boiling point elevation is $62.60°C - 61.20°C = 1.40°C$, and $K_b = 3.63°C/m$, we can solve for $m$, the molality of the solution. $m = \frac{\Delta T_b}{K_b} = \frac{1.40°C}{3.63°C/m} = 0.3855 m$. Molality is moles of solute per kilogram of solvent, so $0.3855 mol/kg = \frac{moles\ of\ hexachlorophene}{0.125 kg}$. Solving for moles of hexachlorophene gives $0.04819 mol$. Using the molar mass of hexachlorophene (406.9 g/mol), the mass of hexachlorophene needed is $0.04819 mol \times 406.9 g/mol = 19.6 g$.

Hexachlorophene Is Used as a Disinfectant in Germicidal Soaps