Freezing-point depression definition

This relationship constitutes the basic definition of the activity. If the solution behaves ideally, a, =x, and Equation (18) define Raoult s law. Those four solution properties that we know as the colligative properties are all based on Equation (12) in each, solvent in solution is in equilibrium with pure solvent in another phase and has the same chemical potential in both phases. This can be solvent vapor in equilibrium with solvent in solution (as in vapor pressure lowering and boiling point elevation) or solvent in solution in equilibrium with pure, solid solvent (as in freezing point depression). Equation (12) also applies to osmotic equilibrium as shown in Figure 3.2. 

Phase diagrams from freezing point depressions show true compound formations for simpler amides—e.g., water-N-methylacetamide forms a compound at a mole ratio of 2 to 1, water-N,N-dimethylacetamide at 3 to 2 and 3 to 1, and water-N-methylpyrrolidone at 2 to 1. The heats of mixing and heat capacities at 25°C. of a number of water-amide systems were determined. All mixing curves were exothermic and possess maxima at definite mole ratios, while the heat capacities for the most part show distinct curvature changes at the characteristic mole ratios. Both experimental results point to the stability of the particular complexes even at room temperature. This is further supported by absolute viscosity studies over the whole concentration range where large maxima occur at these same mole ratios for disubsti-tuted amides and N-substituted pyrrolidones. 

Suppo.se that a colligative property of the polymer solution is measured. These are properties that depend on the number of dissolved solute molecules and not on their sizes (see also Section 2.10). Osmotic pressure, vapor pressure lowering, and freezing point depression are some examples of colligative properties. If the value of the property measured is P, then by definition... 

By definition, E gram of sodium chloride MW = 58.45 and L so = 3.4) in 1 L will have similar freezing-point depression as shown below ... 

Definitions. Define briefly (a) mole fraction, (b) molality, (c) molarity, (d) solubility, (e) saturated solution, (f) supersaturated solution, (g) ideal solution, (h) activity, (i) colligative property, (j) freezing-point depression, (k) osmotic pressure. 

For the special case in which x is chosen equal to M and V = ice, it is evident that AT = 1863° This is the so-called Molecular depression of freezing point For 1 mole dissolved in 1 liter of water, the lowering of freezing point is evidently 1 863° C This agrees excellently with that found by Raoult Note, however, that Raoult s definition of molecular lowering refers to x mole dissolved in 1 gram of solvent, and similarly for the molecular rise of boiling point... 

The simplest explanation of the results of Raoult, Hittorf and Kohlrausch wojidd be that a salt in solution exists more or less in the form of free electrically charged ions, which move so as to form the current through the solution when a potential difference is applied. Since the number of particles in a given volume is increased by ionisation, the abnormally high osmotic pressures and the related abnormal depressions of freezing>point are simply explained. This theory of electrolytic dissociation was first definitely stated by Arrhenius in 1887, ultimately based on the experimental fact that solutions which... 

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