Osmotic pressure of ions

In the polyelectrolyte regime, due to the presence of low-molecular salt, the osmotic pressure of ions becomes less pronounced because the concentration of salt within the network turns out to be less than the concentration of salt in the outer solution n [27]. As the concentration ns grows, the amplitude of the jump of the dependence a(x) decreases and the jump shifts to the region of better solvents (Fig. 2, curve 2). At some critical value of n, the jump on the curve a(x) disappears, i.e. collapse of the network becomes smooth (Fig. 2, curve 3). Under the subsequent increase of n, the curve a(x) becomes closer and closer to the swelling curve of corresponding neutral network (Fig. 2, curves 4). 

We now proceed to take up in a httle more detail the two lines of investigation, or modes of treatment referred to above In doing so, it is to be clearly understood that the sections headed—Degree of Dissociation and the numerical value of the equivalent conductivity at infinite dilution, Osmotic Pressure and concentration in solutions of electrolytes and the calculation of the degree of ionisation, Reaction Velocity m relation to the osmotic pressure of ions and molecules, Ionisation in formic acid solutions—-these sections belong to the first mode of treatment of strong electrolytes, whilst the remaining sections are illustrative of the second method... 

The above relationship for electrostatic component of disjoining pressure has the following meaning the first term, in agreement with eq. (III.20), represents the osmotic pressure of ions in the center of a gap, while the second term is the osmotic pressure in the bulk of dispersion medium. One may thus say that the electrostatic component of disjoining pressure equals to the difference in osmotic pressure between the gap and the bulk, that forces the dispersion medium to flow into the gap between surfaces causing a disjoining action. For small values of (p(h/2) the expansion of hyperbolic cosine into series as cosh (y) 1 + A (y)2 readily yields eq. (V1I.21). 

An increase in concentration Oion of added salt ions, leads to the penetration of salt ions into the star interior and a decrease in the differential osmotic pressure. When the concentration of added ions sufficiently exceeds the average concentration of counterions in the osmotic star, the polyion is found in the so-called salt-dominated regime. Here, the differential osmotic pressure of ions is equivalent to that created by binary monomer-monomer interactions with an effective second viral coefficient Ueff = a /24>ion. As a result, one recovers the same scaling dependence for the size of a PE star as that found for neutral star polymer under good solvent conditions, (4), with replacement u —> Uetr ... 

Ability to hold water = (osmotic pressure of ions... 

According to this equation, it can be seen that the lower the osmotic pressure of ions (the higher the ionic concentration of electrolyte solution) the lower the ability to absorb water. When gels are used in feminine products or as water absorption agents, it is important to select application-specific gels. For feminine products, thirmess and dryness are required. These requirements are accomplished by using absorbent layers [3-5]. 

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). 

C12-0101. Brackish water, with a salt content around 0.5% by mass, is found in semiarid regions such as the American southwest. Assuming that brackish water contains only sodium chloride and that the ions form no ion pairs, estimate the osmotic pressure of brackish water at 298 K. 

Assuming that each ion acts independently of all the others and that seawater has a density of 1.026 g/mL, calculate the freezing point and osmotic pressure of seawater. The actual freezing point of seawater is - 1.96 ° C. What conclusion can you reach about your assumptions Take this into account and recalculate the osmotic pressure of seawater. 

The osmotic pressure of an electrolyte solution jt can be considered as the ideal osmotic pressure jt decreased by the pressure jrel resulting from electric cohesion between ions. The work connected with a change in the concentration of the solution is n dV = jt dV — jrel dV. The electric part of this work is then JteldV = dWcl, and thus jzc] = (dWei/dV)T,n. The osmotic coefficient 0 is given by the ratio jt/jt, from which it follows that... 

Calculations Membrane transport Chemical reaction networks Osmotic pressure and ion transport thermodynamics Extending the idea of chemical networks to extreme environments of temperature and pressure to discover autotrophs... 

Since osmotic pressure depends upon the number of particles of solute(s) in solution, the osmotic pressure of an electrolyte is directly proportional to the degree (or extent) of dissociation. The dissociation factor, symbolized by the letter i, can be calculated by dividing the total number of particles (which include undissociated molecules and ions) in a solution by the number of particles before dissociation, i.e.,... 

Electrolytes regulate body water volumes by establishing osmotic pressure which is proportional to the total number of particles in solution. The osmotic pressure of a solution is expressed in units of milliosmoles (mOsm). Osmolar concentrations reflects the number of particles (molecules as well as ions) of total solutes per volume of solution, which in turn determines the osmotic pressure of the solution. 

Mecftanism of Action Sodium Is a major cat ion of extracellular fluid that controls water distribution, fluid and electrolyte balance, and osmotic pressure of body fluids it also maintains acid-base balance. 

If you have a class with biochemists, clearly the area of enzyme kinetics is practically mandatory. If biologists are mixed in with the biochemists, osmotic pressure is an important concept to cover carefully and a concept typically not well covered in general chemistry and in most physical chemistry texts or classes. A quick example what is a 2 Osmolar solution of sodium chloride Such concentration units are used when dispensing various saline solutions in hospitals. What is the origin of the unit A 1 M NaCl solution dissociates into two ions that would double the osmotic pressure of a non dissociating solute. Thus, the 1 M solution of NaCl becomes a 2 Osmolar solution. Other examples abound - the bursting pressure of a cell relates to the osmotic pressure of the serum in which the cell finds itself. 

It is important to note that the concept of osmotic pressure is more general than suggested by the above experiment. In particular, one does not have to invoke the presence of a membrane (or even a concentration difference) to define osmotic pressure. The osmotic pressure, being a property of a solution, always exists and serves to counteract the tendency of the chemical potentials to equalize. It is not important how the differences in the chemical potential come about. The differences may arise due to other factors such as an electric field or gravity. For example, we see in Chapter 11 (Section 11.7a) how osmotic pressure plays a major role in giving rise to repulsion between electrical double layers here, the variation of the concentration in the electrical double layers arises from the electrostatic interaction between a charged surface and the ions in the solution. In Chapter 13 (Section 13.6b.3), we provide another example of the role of differences in osmotic pressures of a polymer solution in giving rise to an effective attractive force between colloidal particles suspended in the solution. 

At x > xcr, the network is in the very expanded state. The size of the chain between two junction points, R, is proportional to m R = aR0 ma/a /2 as it is for fully stretched chain. The reason for such an essential expansion is the osmotic pressure of counter ions which originates from their translational entropy. Trom the entropy consideration counter ions would like to leave the network, however, this is forbidden due to the condition of total electroneutrality. This effect was for the first time described in Ref. [7]. 

The isoelectric regime (ct, > a3 Fig. 1, curve 3). Here the network remains in compressed state even in good solvent a. m-1/6. The attractive electrostatic interaction due to the term Fei s, < 0 (see Eq. (9)) and very small osmotic pressure of counter ions due to their low concentration are the reasons. 

The list of the new gels for which phase transitions are possible is supplemented in the paper by Amiya and Tanaka, who discovered discrete collapse for the most important representatives of biopolymers - chemically crosslinked networks formed by proteins, DNA and polysaccharides [45]. Thus, it was demonstrated that discrete collapse is a general property of weakly charged gels and that the most important factor, which is responsible for the occurrence of this phenomenon, is the osmotic pressure of the system of counter ions. 

The experimental result obtained was explained by the formation of ion pairs between the charges of a network and counter ions. The theoretical analysis of this problem has shown that the degree of ion pairs formation very strongly (exponentially) depends on e (cf. Sect. 2.2). Thus, if the precipitant has a small dielectric constant e (e.g. dioxane) the degree of dissociation of ion pairs is sufficiently small and this fact leads to the decrease of the osmotic pressure of counter ions which defines the swelling of the gel and the point of the transition in the collapsed state. As a result, in this case the degree of swelling of the gel near the transition point is less pronounced than for other solvents and only a relatively small amount of the precipitant is required to reach this point. In... 

Halorhodopsiti. In addition to bacteriorhodopsin there are three other retinal-containing proteins in membranes of halobacteria. From mutant strains lacking bacteriorhodopsin the second protein, halorhodopsin, has been isolated. It acts as a light-driven chloride ion pump, transporting Cl from outside to inside. Potassium ions follow, and the pump provides a means for these bacteria to accumulate KC1 to balance the high external osmotic pressure of the environment in which they live.578 The amino acid sequences of halorhodopsins from several species are very similar to those of bacteriorhodopsin as is the three-dimensional structure.589 However, the important proton-carrying residues D85 and D96 of bacteriorhodopsin are replaced by threonine and alanine, respectively, in halorhodopsin.590 Halorhodopsin (hR)... 

The osmotic pressure of brackish water is approximately 11 psi per 1000 ppm salt, so osmotic pressure effects do not generally limit water recovery significantly. Limitations are generally due to scaling. Typical water recoveries are in the 70-90 % range, which means the brine stream leaving the system is up to 10 times more concentrated in calcium, sulfate and silica ions present in the feed. If scaling occurs, the last modules in the system must be replaced first. 

The osmotic pressure of a solution of non-interacting molecules or ions at the zero concentration limit is determined by the total molar concentration of solute species. In this hypothetical state, a solution of a polyelectrolyte may contain highly charged polyions at concentration c and monovalent counterions at a concentration where c is the molar concentration of the polyelectrolyte and z is the number of counterions per polyion. Since the total molar concentration is c (z +1) c z for z l, the ideal osmotic pressure is... 

If 9.45 grams of chloracetic acid, H(C2H202C1), dissolved in 1,000 grams of water show an osmotic pressure of 2.51 atmospheres, find the per cent ionization of the acid, assuming that only one hydrogen is ionizable and that the negative ion has the composition of the radical shown in the parenthesis. 

---