Aqueous solutions Freezing point

Ethylenedlamlnes Aqueous Solutions, Freezing Point vs. Composition... 

Freezing point depression 0.14°C (1% w/v aqueous solution) Melting point decomposition at 252°C for the dihydrate. Refractive index 1.33 (1% w/v aqueous solution)... 

This paper reports cryoscopic measurements for NiS04 aqueous solutions in saturated potassium chlorate solution (freezing point 272.55 K) and saturated potassium nitrate solution (freezing point 270.32 K). The eutectic freezing point depressions, AT, are between 0.0296 K and 0.178 K. Thus, together with the measurements reported in [56KEN], the variation in the complexation constant, K, with ionic strength was examined. 

Some physical properties of solutions differ in important ways from those of the pure solvent. For example, pure water freezes at 0 °C, but aqueous solutions freeze at lower temperatures. We utilize this behavior when we add ethylene glycol antifreeze to a car s radiator to lower the freezing point of the solution. The added solute also raises the boiling point of the solution above that of pure water, making it possible to operate the engine at a higher temperature. 

Fig. 2. Freezing points of aqueous glycol solutions. A, ethylene glycol B, diethylene glycol C, triethylene glycol and D, tetraethylene glycol. Ethylene glycols...

Potassium hydroxide is the principal electrolyte of choice for the above batteries because of its compatibiUty with the various electrodes, good conductivity, and low freezing point temperature. Potassium hydroxide is a white crystalline substance having a mol wt = 56.10 density = 2.044 g/mL, and mp = 360° C (see Potassium compounds). It is hygroscopic and very soluble in water. The most conductive aqueous solution at 25 °C is at 27% KOH, but the conductivity characteristics are relatively flat over a broad range of concentrations. 

Commercial appHcations of calcium chloride and its hydrates exploit one or more of its properties with regard to aqueous solubiUty, hygroscopic nature, the heat gained or lost when one hydrated phase changes to another, and the depressed freezing point of the eutectic solution at a composition of about 30% by weight calcium chloride. 

Figure 11-16. Freezing points of aqueous solutions of ethylene and propylene glycol. (Used by permission 1977ASHRAEHandbook, l-P Ed., Fundamentals, 1979 ASHRAE Handbook and Product Directory, 1979,1980 2"= printing, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. All rights reserved.)...

The internal structure of a liquid at a temperature near its freezing point has been discussed in Sec. 24. Each molecule vibrates in a little cage or cell, whose boundaries are provided by the adjacent molecules, as in Fig. 20, and likewise for each solute particle in solution in a solvent near its freezing point. It is clear that the question of the hydration of ions no longer arises in its original form. In aqueous solution an atomic ion will never be in contact with less than three or four water molecules, which in turn will be in contact with other water molecules, and so on. There is an electrostatic attraction, not only between the ion and the molecular dipoles in immediate contact with it, but also between the ion and molecular dipoles that are not in contact with it. For solvent dipoles that are in contact with a small doubly charged ion, such as Ca++,... 

The freezing points of electrolyte solutions, like their vapor pressures, are lower than those of nonelectrolytes at the same concentration. Sodium chloride and calcium chloride are used to lower the melting point of ice on highways their aqueous solutions can have freezing points as low as —21 and — 55°C, respectively. 

Estimate the freezing and normal boiling points of 0.25 m aqueous solutions of... 

What is the freezing point of vinegar, which is an aqueous solution of 5.00% acetic acid, HC2H3O2, by mass (d = 1.006 g/cm3) ... 

The ionisation may be attributed to the great tendency of the free hydrogen ions H+ to combine with water molecules to form hydroxonium ions. Hydrochloric and nitric acids are almost completely dissociated in aqueous solution in accordance with the above equations this is readily demonstrated by freezing-point measurements and by other methods. 

A similar method was used in connexion with the lowering of vapour pressure in 130. It is evident that, since the factor i was introduced in the same connexion in both investigations, the values of i obtained by both methods, viz., by measurements of vapour pressure and of freezing-point, are necessarily the same, and their agreement is therefore independent of any theory which we may adopt to explain the anomalous behaviour of aqueous salt solutions. 

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 ... 

Freezing point methods are often applied to the measurement of activities of electrolytes in dilute aqueous solution because the freezing point lowering, 6= T — T, can be determined with high accuracy, and the solute does not dissolve in the solid to any appreciable extent. Equations can be derivedgg relating a to 9 instead of T and T. The detailed expressions can be found in the literature.16... 

Determine the freezing point of a 0.10 mol-kg aqueous solution of a weak electrolyte that is 7.5% dissociated into two ions. 

Colligative properties can be sources of insight into not only the properties of solutions, but also the properties of the solute. For example, acetic acid, CH.COOH, behaves differently in two different solvents, (a) The freezing point of a 5.00% by mass aqueous acetic acid solution is — l.72°C. What is the molar mass of the solute Explain any discrepancy between the experimental and the expected molar mass, (b) The freezing-point depression associated with a 5.00% by mass solution of acetic acid in benzene is 2.32°C. Whar is the experimental molar mass of the solute in benzene What can you conclude about the nature of acetic acid in benzene ... 

C12-0069. List the following aqueous solutions in order of decreasing freezing point, and explain your listing 0.30 M NaCl, 0.75 M NH3,0.25 M MgCl2,0.25 M NH3. ... 

C12-0074. The freezing point of an aqueous solution containing pantothenic acid... 

C12-0097. When an aqueous solution cools to low temperature, part of the water freezes as pure ice. What happens to the freezing point of the remaining solution when this occurs A glass of wine placed in a freezer at -10 C for a very long time forms some ice crystals but does not completely freeze. Compute the molality of ethanol in the remaining liquid phase. 

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