Aqueous solutions osmotic pressure

Pfeffer deposited a copper ferrocyanide membrane in the walls of a porous clay pot. This was filled with the solution to be investigated, attached to a mercury manometer, and immersed in water. Some water entered the pot and the pressure increased, reaching a maximum value, called the osmotic pressure. The pressures were high, more than 3 atm. for a solution of 1 5 per cent, of potassium nitrate. Ladenburg and R. H. Adie confirmed Pfeffer s main results, and Raoult obtained a pressure of 50 atm. with ether and methyl alcohol and a vulcanised rubber membrane. Measurements with aqueous solutions, at pressures higher than those reached by Pfeffer, were made by H. N. Morse and collaborators and the Earl of Berkeley and E. G. J. Hartley. ... 

Ophthalmic Dosage Forms. Ophthalmic preparations can be solutions, eg, eye drops, eyewashes, ointments, or aqueous suspensions (30). They must be sterile and any suspended dmg particles must be of a very fine particle size. Solutions must be particle free and isotonic with tears. Thus, the osmotic pressure must equal that of normal saline (0.9% sodium chloride) solution. Hypotonic solutions are adjusted to be isotonic by addition of calculated amounts of tonicity adjusters, eg, sodium chloride, boric acid, or sodium nitrate. 

Table 3. Osmotic Pressure of Aqueous Sucrose Solutions at 25°C ...

For example, in the case of dilute solutions, the van t Hoff s equation may be used to piedict the osmotic pressure (jr = CRT) where n is the osmotic pressure of the solution, C is the molar concentration of the solute, ft is the universal gas constant and T is the absolute temperature, Fm dissociating solutes, the concentration is that of the total ions. For example, NaCI dissociates in water into two ions Na" " and Cl . Therefore, the total molar concentration of ions is hvice the molar concentration of NaCI. A useful rule of thumb for predicting osmotic pressure of aqueous solutions is 0,01 psi/ppm of solute (Weber, 1972). 

Molar masses can also be determined using other colligative properties. Osmotic pressure measurements are often used, particularly for solutes of high molar mass, where the concentration is likely to be quite low. The advantage of using osmotic pressure is that the effect is relatively large. Consider, for example, a 0.0010 M aqueous solution, for which... 

Solutions introduced directly into the bloodstream have to be isotonic with blood that is, they must have the same osmotic pressure as blood. An aqueous NaCl solution has to be 0.90% by mass to be isotonic with blood. What is the molarity of sodium ions in solution Take the density of the solution to be 1.00 g/mL. 

Insulin is a hormone responsible for the regulation of glucose levels in the blood. An aqueous solution of insulin has an osmotic pressure of 2.5 mm Hg at 25°C. It is prepared by dissolving 0.100 g of insulin in enough water to make 125 mL of solution. What is the molar mass of insulin ... 

What is the density of an aqueous solution of potassium nitrate that has a normal boiling point of 103.0°C and an osmotic pressure of 122 atm at 25°C ... 

An alternative method of purifying water is by reverse osmosis. Under normal conditions, if an aqueous solution is separated by a semi-permeable membrane from pure water, osmosis will lead to water entering the solution to dilute it. If, however, sufficient pressure is applied to the solution, i.e. a pressure in excess of its osmotic pressure, then water will flow through the membrane from the solution the process of reverse osmosis is taking place. This principle has been... 

Table 7.3 Osmotic pressures of aqueous sucrose solutions at T = 293.15 K...

E7.14 Estimate the vapor pressure lowering and the osmotic pressure at 293.15 K for an aqueous solution containing 50.0 g of sucrose (Mi = 0.3423 kg-mol"1) in 1 kg of water. At this temperature, the density of pure water is 0.99729 g em"3 and the vapor pressure is 2.33474 kPa. Compare your results with those given in Table 7.3. 

C12-0071. An aqueous solution contains 1.00 g/L of a derivative of the detergent lauryl alcohol. The osmotic pressure of this solution at 25.0 °C is measured to be 64.8 torr. (a) What is the molar mass of the detergent (b) The hydrocarbon portion of the molecule is an 11-carbon chain. What is the molar mass of the polar portion ... 

Numerous measurements of the conductivity of aqueous solutions performed by the school of Friedrich Kohhansch (1840-1910) and the investigations of Jacobns van t Hoff (1852-1911 Nobel prize, 1901) on the osmotic pressure of solutions led the young Swedish physicist Svante August Arrhenius (1859-1927 Nobel prize, 1903) to establish in 1884 in his thesis the main ideas of his famous theory of electrolytic dissociation of acids, alkalis, and salts in solutions. Despite the sceptitism of some chemists, this theory was generally accepted toward the end of the centnry. 

Rard (1992) reported the results of isopiestic vapor-pressure measurements for the aqueous solution of high-purity NiCl2 solution form 1.4382 to 5.7199 mol/kg at 298.1510.005 K. Based on these measurements he calculated the osmotic coefficient of aqueous NiCb solutions. He also evaluated other data from the literature and finally presented a set of smoothed osmotic coefficient and activity of water data (see Table IV in original reference). 

The activity coefficient of the solvent remains close to unity up to quite high electrolyte concentrations e.g. the activity coefficient for water in an aqueous solution of 2 m KC1 at 25°C equals y0x = 1.004, while the value for potassium chloride in this solution is y tX = 0.614, indicating a quite large deviation from the ideal behaviour. Thus, the activity coefficient of the solvent is not a suitable characteristic of the real behaviour of solutions of electrolytes. If the deviation from ideal behaviour is to be expressed in terms of quantities connected with the solvent, then the osmotic coefficient is employed. The osmotic pressure of the system is denoted as jz and the hypothetical osmotic pressure of a solution with the same composition that would behave ideally as jt. The equations for the osmotic pressures jt and jt are obtained from the equilibrium condition of the pure solvent and of the solution. Under equilibrium conditions the chemical potential of the pure solvent, which is equal to the standard chemical potential at the pressure p, is equal to the chemical potential of the solvent in the solution under the osmotic pressure jt,... 

Diluted or concentrated rinsewaters are circulated through the membrane at pressures greater than aqueous osmotic pressure. This action results in the separation of water from the plating chemicals. The recovered chemicals can be returned to the plating bath for reuse, and the permeate, which is similar to the condensate from an evaporator, can be used as make-up water. RO units work best on dilute solutions.30... 

It was Brown and Morris (15) in 1888 who employed Raoult s method. They reported a value of 30,000 for the molecular weight of amylodextrin, a degradation product of the hydrolysis of starch. Subsequently Lintner and Dull (16) also using cryoscopy reexamined amylodextrin, and reported the molecular weight as 17,500. In a third paper, Rodewald and Kattein (17) in 1900, measured the molecular weight of starch by osmotic pressure experiments carried out on aqueous solutions of starch iodide. They obtained somewhat higher molecular weights, 36,700 and 39,700. 

See Kragh, "Between Physics and Chemistry," 27 and Barkan, "Walther Nemst," 158159, drawing on a letter from Ostwald to Nerst, 22 November 1892, Ostwald Papers, AAW, Berlin. The views at issue are found in J. H. van t Hoff, "Role of Osmotic Pressure in the Analogy between Solutions and Gases" (1887) and Svante Arrhenius, "On the Dissociation of Substances in Aqueous Solution" (1887), in The Foundations of the Theory of Dilute Solution (Edinburgh Alembic Club, 1929), no. 19. 

It is illuminating to quote some early results on aqueous sucrose solutions obtained by Maron and Lou36. They demonstrate clearly the complimentarity between osmotic pressure and LS. Reference to Eqs. (34) and (35) shows that... 

For purposes of illustration, the following discussion, unless otherwise specified, is limited to single-solute aqueous feed solutions, cellulose acetate membranes, and reverse osmosis systems for which osmotic pressure effects are essentially negligible. 

For an aqueous solution at 0° 0. showing an osmotic pressure of one hundred atmospheres we find... 

One more boimdary condition is required to specify the problem. Suppose that the rate of myelin growth is directly proportional to the osmotic pressure difference Ap between the bulk aqueous solution and the lamellar phase at the base of the myelins (x = 0) and inversely proportional to myehn length. For example, contact between the myelins could provide resistance to the swelling process proportional to myelin length. Hence... 

The electrostatic potential at a distance of 5nm away from a charged, flat surface was found to be -10 mV in an aqueous 0.1 mM NaCl solution. Estimate the electrostatic potential at the surface. What are the concentrations of each ion at this distance away from the surface Estimate the osmotic pressure at this plane. 

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