Colligative properties defined

The lowering of the vapour pressure of a pure liquid A by the addition of B (as above) is one example of a colligative property (defined in Frame 51) where such properties are further discussed and include ... 

How are colligative properties defined and what are three major colligative properties ... 

C12-0027. Define and give an example of each of the following (a) alloy (b) amalgam (c) aerosol (d) colligative property and (e) surfactant. 

Of the preponderance of small ions, the colligative properties of polyelectrolytes in ionising solvents measure counterion activities rather than Molecular weight. In the presence of added salt, however, correct Molecular weights of polyelectrolytes can be measured by membrane osmometry, since the small ions can move across the membrane. The second virial coefficient differs from that previously defined, since it is determined by both ionic and non-ionic polymer-solvent interactions. 

One important aspect of solutions is their concentration, the amount of solute dissolved in the solvent. In the chapter on solutions and colligative properties we will cover several concentration units, but for the purpose of stoichiometry, the only concentration unit we will use at this time is molarity. Molarity (M) is defined as the moles of solute per liter of solution ... 

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. 

Another way of expressing concentrations that is used commonly with gases (see p 162) and colligative properties (see p 328) is mole fraction, which is defined (for a given component) as being the moles of component in question divided by the total moles of all components in solution. For a solution that has three components (A, B, and C), the mole fraction of A is given by... 

Equation (2-62) is the key to the application of colligative properties to polymer molecular weights. We started with Eq. (2-53), which defined an ideal solution in terms of the mole fractions of the components. Equation (2-62), which followed by simple arithmetic, expresses the difference in chemical potential of the solvent in the solution and in the pure state in terms of the mass concentrations of the solute. This difference in chemical potential is seen to be a power series in the solute concentration. Such equations are called virial equations and more is said about them on page 65. 

It should be stressed that such condensation of counterion by polyion is determined just by the structural parameter that defines charge density along the length of the macromolecule. It is not influenced by external condition, such as Cp or the addition of salt. The fact that the colligative properties of salt and polyelectrolyte are found to be additive [32,33] when salt is added to the polyelectrolyte provides insight with respect to the uniqueness of ( )p and y,. Such behavior is attributable to the inaccessibility of the polyion, the condensed Na" " ions and the solvent associated with the polyion domain, to the measurements being carried out. Their presence as a separate phase, however, is not detectable by the counterion activity measurement in the absence of simple salt. 

Let us focus attention on the simple 1 1 electrolyte H+Cr. Its activity a, as a compound, may be found from colligative properties, but the activities of the ions, a and a, are not determinable separately. These ionic activities must first be carefully defined in terms of a reference state with unit fugacity as before, a f-/f- The reference states are defined such that, for the equation ... 

Define the term osmotic pressure, and explain why it is considered a colligative property. 

Osmotic pressure is also a colligative property. Before we talk about osmotic pressure let s turn our attention to the process of osmosis. Consider two solutions that are made out of the same solvent with different concentrations of solute separated by a semipermeable membrane. The solvent will flow through the semipermeable membrane from the solution of lower concentration to the solution of higher concentration. Thus, osmosis is defined as the flow of solvent through a semipermeable membrane resulting in the equilibrium of concentrations on both sides of the semipermeable membrane. 

A colligative property is defined as one that is a function of the number of solute molecules present per unit volume of solution and is unaffected by the chemical nature of the solute. Thus, if Y represents any of the aforementioned colligative properties, then... 

The osmotic pressure is an important colligative property of the polymer solution, which can be directly measrtred in experiment. It is defined as... 

Define ion pairs. What effect does ion-pair formation have on the colligative properties of a solution How does the ease of ion-pair formation depend on (a) charges on the ions, (b) size of the ions,... 

Certain solutes produce a greater effect on colligative properties than expected from the relations given in Section 4.4. This can be allowed for empirically by introducing the van t Hofffactor (/), which is defined as... 

A strong electrolyte is defined by two observations (1) the value of i measured by colligative properties equals the number of ion types that would be expected from complete dissociation (for NaCl, i = 2 for Na2S04, i = 3, etc.), and (2) doubling the electrolyte concentration leads to a doubling of the con-... 

So far we have discussed the colligative properties of nonelectrolyte solutions. Because electrolytes undergo dissociation when dissolved in water [W Section 4.1], we must consider them separately. Recall, for example, that when NaCl dissolves in water, it dissociates into Na Co ) and C aq). For every mole of NaCl dissolved, we get two moles of ions in solution. Similarly, when a formula unit of CaCL dissolves, we get three ions one Ca ion and two Cl ions. Thus, for every mole of CaCl2 dissolved, we get three moles of ions in solution. Colligative properties depend only on the number of dissolved particle.s—not on the type of particles. This means that a 0.1 m solution of NaCl will exhibit a freezing point depression twice that of a 0.1 m solution of a nonelectrolyte, such as sucrose. Similarly, we expect a 0.1 m solution of CaCL to depress the freezing point of water three times as much as a 0.1 m sucrose solution. To account for this effect, we introduce and define a quantity called the van t Hoff factor (i), which is given by... 

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. 

Before considering the next colligative properties, we recall the concentration unit molality. The molality of a solution is similar to molarity except that it is defined in terms of the number of kilograms of solvent, not liters of solution ... 

Molality, abbreviated molal or m, is useful for colligative properties because it is a more direct ratio of molecules of solute to molecules of solvent. The unit molarity automatically includes the concept of partial molar volumes because it is defined in terms of liters of solution, not liters of solvent. It is also dependent on the amounts of solvent and solute (in mole and kilogram units), but independent of volume or temperature. Thus, as T changes, the concentration in molality units remains constant while the concentration in molarity units varies due to expansion or contraction of the solutions volume. 

The next colligative property is boiling point elevation. A pure liquid has a well-defined boiling point at a particular pressure. If a nonvolatile solute were added, then to some extent those solute molecules would impede the ability of solvent molecules to escape from the liquid phase, so more energy is required to make the liquid boil, and the boiling point increases. 

---