Ionic solutions colligative properties

Because of electrostatic attraction, an ion in solution tends to surround itself with more ions of opposite than of like charge (Figure 10.12). The existence of this ionic atmosphere, first proposed by Peter Debye (1884-1966), a Dutch physical chemist in 1923, prevents ions from acting as completely independent solute particles. The result is to make an ion somewhat less effective than a nonelectrolyte molecule in its influence on colligative properties. 

The second period, from 1890 to around 1920, was characterized by the idea of ionic dissociation and the equilibrium between neutral and ionic species. This model was used by Arrhenius to account for the concentration dependence of electrical conductivity and certain other properties of aqueous electrolytes. It was reinforced by the research of Van t Hoff on the colligative properties of solutions. However, the inability of ionic dissociation to explain quantitatively the properties of electrolyte solutions was soon recognized. 

Osmotic pressure, a colligative property, depends on the concentration of solute (neutral molecule or ionic species) that contributes to the osmotic pressure. Solutions of different concentrations having the same solute and solvent system exhibit an osmotic pressure proportional to their concentrations. Thus a constant osmotic pressure, and thereby a constant influx of water, can be achieved by an osmotic delivery system that results in a constant release rate of drug. Therefore, zero-order release, which is important for a controlled release delivery system when indicated, is possible to achieve using these platforms. In 1974,... 

Evidence for dimerization of the hydroxoaqua ion is based on the decrease of the number of chromium particles in reaction 10 and its increase in reaction 11. The number, v, of discrete chromium particles per diaqua ion should decrease from v = 1 to v = as the diaqua ion is titrated with 1 mol of OH" and then rise again to v = 1 as a second mole of OH" is added, v may be determined by measuring a colligative property of the solution. A most suitable method for ionic solutes is Three-Phase Vapor Tensiometry, TPVT i The three-phase solvent system consists of a saturated solution of an electrolyte in water, in equilibrium with the crystalline phase of that electrolyte and with water vapor. An isobaric temperature difference (AT)p is established when the pure solvent is equilibrated with a solution of a foreign solute in the same solvent, at constant pressure. The apparent number, Vm of free particles per formula of solute depends on the molality of the solute (m), the three-phase ebulioscopic constant Kg, and (AT)p... 

For solutions that contain electrolytes, the change from the pure solvent to a solution is different from what is predicted by the above equations. Due to their ionic nature, these substances will dissociate to put many more ions in solution than their molal concentration would predict. The total number of ions affects the colligative properties just as the number of molecules would for a nonpolar solute. 

Compare and contrast the ability of water to dissolve ionic and covalent compounds. Distinguish solutions from colloids. Compare and contrast colligative properties. 

The solutes whose structure in the solid is a giant ionic lattice give strongly conducting solutions whose colligative properties place them in category (a). Colours of ionic solutions... 

This has always been an important, though very indirect, source of hydration numbers. Colligative properties and emfs give high precision experimental data from which the activity of the solute can be calculated and stoichiometric mean ionic activity coefficients found. If it is assumed that solvent molecules are bound to the ions, a relation between... 

Ionic solutes are dissociated in solution into cations and anions. Thus aim aqueous solution of NaCl contains 1 mol of Na ions and 1 mol of Cl ions per kilogram of solvent. There are 2 mol of particles per kilogram of solvent, and therefore the colligative properties of the solution are greater than those of a 1 m solution of nonionic solute. In very dilute solutions, the colligative properties of solutions of ionic solutes are a multiple of the analogous properties of nonionic solutes. For example,... 

Colligative properties are related to the number of dissolved solute particles, not their chemical nature. Compared with the pure solvent, a solution of a nonvolatile nonelectrolyte has a lower vapor pressure (Raoult s law), an elevated boiling point, a depressed freezing point, and an osmotic pressure. Colligative properties can be used to determine the solute molar mass. When solute and solvent are volatile, the vapor pressure of each is lowered by the presence of the other. The vapor pressure of the more volatile component is always higher. Electrolyte solutions exhibit nonideal behavior because ionic interactions reduce the effective concentration of the ions. 

Ionic solutions are formed when the solute ionizes in water. The ions of the molecule separate in water and are surrounded or hydrated by the water molecules. Ionic molecules greatly influence the mobility of water molecules surrounding them and affect the colligative properties of solvent water. The degree to which the structure of bulk water is disrupted depends on the valence, size, and concentration of the ion in solution. In ice, the presence of ions interferes with intermolecular forces between water molecules and disrupts the crystal lattice structure. Hence the presence of salt decreases the melting point of water. 

Usha Of course, Racheli Haven t you heard about colligative properties of ionic versus covalent solutions ... 

The total concentration of all dissolved solute species determines the colligative properties. As we will emphasize in Section 14-14, we must take into account the extent of ion formation in solutions of ionic solutes. 

One measure of the extent of dissociation (or ionization) of an electrolyte in water is the van t Hoff factor,, for the solution. This is the ratio of the actual colligative property to the value that would be observed if no ionic dissociation occurred. 

We start with solutions of nonvolatile nonelectrolytes because they provide the clearest examples of the colligative properties. These solutions contain solutes that are not ionic and so do not dissociate, and they have negligible vapor pressure at the boiling point of the solvent sucrose (table sugar) dissolved in water is an example. 

Given the concentration of ionic compound in a solution, calculate the magnitude of a colligative property if i is not given, assume the value based on the formula of the ionic compound. (EXAMPLE 12.14)... 

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