Boiling point elevation constant nonelectrolyte

Solutions containing nonelectrolyte nonvolatile solutes have higher boiling points than the pure solvent. The boiling point elevation (ATb) is directly proportional to the solvent s boiling point elevation constant (Ky) times the molality (m) of the solute in moles per kg of solvent ... 

The molal boiling point elevation constant, S), is the difference in boiling points between aim nonvolatile, nonelectrolyte solution and a pure solvent. It is expressed in units of °C/w and varies for different solvents. Values of A j, for several common solvents are found in Table 15-4. Note that water s A j, value is 0.512°C/w. This means that a m aqueous solution containing a nonvolatile, nonelectrolyte solute boils at 100.512°C, a temperature 0.512°C higher than pure water s boiling point of 100.0°C. 

Boiling point elevation constant, A constant that corresponds to the change (increase) in boiling point produced by a one-molal ideal solution of a nonvolatile nonelectrolyte. CoUigative properties Physical properties of solutions that depend on the number but not the kind of solute particles present. Colloid A heterogeneous mixture in which solute-like particles do not settle out also called colloidal dispersion. 

Kb is the boiling point elevation constant, and for water equals 0.52°C/m. Each solvent has its own unique value for Kb, and the value of Kb for water indicates that a 1.0 m solution of glucose, a nonelectrolyte, would boil 0.52°C higher than that of pure water, 100.52°C. As with the equation used to calculate freezing point depressions, if the solute is an electrolyte, the molality of the ions will be a whole number multiple of the molality of the compound. 

Molar mass determination by freezing-point depression or boiling-point elevation has its limitations. Equations (14.5) and (14.6) apply only to dilute solutions of nonelectrolytes, usually much less than 1 mol kg . This requires the use of special thermometers so that temperatures can be measured very precisely, say to 0.001 °C. Because boiling points depend on barometric pressure, precise measurements require that pressure be held constant. As a consequence, boiling-point elevation is not much used. The precision of the freezing-point depression method can be improved by using a solvent... 

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