Understanding the Concepts
* Molality (m): Molality is the number of moles of solute per kilogram of solvent.
* Boiling Point Elevation: When a non-volatile solute (like naphthalene) is dissolved in a solvent (like benzene), the boiling point of the solution increases. This is known as boiling point elevation.
* Boiling Point Elevation Constant (Kb): This constant is specific to the solvent and represents the change in boiling point per molal concentration of solute. For benzene, Kb = 2.53 °C/m.
Calculating the Boiling Point Elevation
1. Use the formula: ΔTb = Kb * m
* ΔTb = change in boiling point
* Kb = boiling point elevation constant (2.53 °C/m for benzene)
* m = molality (2.47 m)
2. Plug in the values: ΔTb = (2.53 °C/m) * (2.47 m) = 6.25 °C
Calculating the Final Boiling Point
1. Add the boiling point elevation to the normal boiling point of benzene:
* Final boiling point = Normal boiling point of benzene + ΔTb
* Final boiling point = 80.1 °C + 6.25 °C = 86.35 °C
Therefore, the boiling point of a 2.47 molal solution of naphthalene in benzene is approximately 86.35 °C.
