Depression of freezing point

Raoult s law When a solute is dissolved in a solvent, the vapour pressure of the latter is lowered proportionally to the mole fraction of solute present. Since the lowering of vapour pressure causes an elevation of the boiling point and a depression of the freezing point, Raoult s law also applies and leads to the conclusion that the elevation of boiling point or depression of freezing point is proportional to the weight of the solute and inversely proportional to its molecular weight. Raoult s law is strictly only applicable to ideal solutions since it assumes that there is no chemical interaction between the solute and solvent molecules. 

The theory of the depression of freezing-point of a solvent by addition of a soluble substance considered in 132 is based on... 

The linear relation between the depression of freezing-point and the concentration strictly applies only to infinite dilution although it holds good approximately up to decinormal concentration. 

J. B. Goebel (Zeitschr. physik. Chem., 53, 213, 1905 54, 314, 1906 71, 652, 1910) has found an empirical equation for the depression of freezing-point in aqueous solutions of total molecular concentration n ... 

Sodium ehloride equivalent, whieh is produced by dividing the value for the depression of freezing-point produced by a solution of the substance by the corresponding value of a solution of sodium chloride of the same strength. 

Elevation of boiling point and depression of freezing point of the solution. Within certain limits, the change in temperature of these phase transitions obeys the eqnation... 

Component Concentration in water (% by wt) Depression of freezing point (° C)... 

The depression of freezing point is dependent on concentration. A mixture of glycol in water will lower the freezing point with an increasing amount of ethylene glycol, as given in Table 14-2. 

It is now time to draw all the threads together, and look at the temperature at which the thin lines intersect. It is clear from Figure 5.18 that the intersection temperature for the mixture occurs at a cooler temperature than that for the pure material, showing why the melting point temperature for a mixture is depressed relative to a pure compound. The depression of freezing point is a direct consequence of chemical potentials as defined in Equation (5.12). 

Dissolving a solute in a solvent causes a depression of freezing point, in the same way as mixing solids. 

On the basis of freezing point depression values, the USP includes a method for rapidly adjusting isotonicity of ophthalmic solutions. Since depression of freezing point depends upon the number of particles of solute(s) in solution, a proportion can be set up to solve for the volume of isotonic solution... 

The depression of freezing point or reduction of the vapour pressure of a solvent is proportional to the molar concentration of the solute. 

The osmotic pressure of a solution is a colligative property, i.e. it is proportional to the number of solute particles present in the solution, rather than to their weight. It is usually determined by measuring another colligative property, the depression of freezing point relative to water. 

Table 2.16 Solvents for molecular weight determination by depression of freezing point...

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