Concentration of a solution

Fig. 23(D) shows a simple distillation apparatus with an adaptor fitted to the lower end of the condenser. This apparatus can also be used for the recovery of solvents, or for the concentration of a solution with collection of the distilled solvent.

In practice, it is more convenient to predict the behavior of an ion, for any chosen set of conditions, by employing a much simpler distribution coefficient, which is defined as the concentration of a solute in the resin phase divided by its concentration in the liquid phase, or ... 

Both molarity and formality express concentration as moles of solute per liter of solution. There is, however, a subtle difference between molarity and formality. Molarity is the concentration of a particular chemical species in solution. Formality, on the other hand, is a substance s total concentration in solution without regard to its specific chemical form. There is no difference between a substance s molarity and formality if it dissolves without dissociating into ions. The molar concentration of a solution of glucose, for example, is the same as its formality. 

Concentration. The basis unit of concentration in chemistry is the mole which is the amount of substance that contains as many entities, eg, atoms, molecules, ions, electrons, protons, etc, as there are atoms in 12 g of ie, Avogadro s number = 6.0221367 x 10. Solution concentrations are expressed on either a weight or volume basis. MolaUty is the concentration of a solution in terms of the number of moles of solute per kilogram of solvent. Molarity is the concentration of a solution in terms of the number of moles of solute per Hter of solution. 

Polarimetric determination of the sucrose concentration of a solution is vaUd when sucrose is the only optically active constituent of the sample. In practice, sugar solutions are almost never pure, but contain other optically active substances, most notably the products of sucrose inversion, fmctose and glucose, and sometimes also the microbial polysaccharide dextran, which is dextrorotatory. Corrections can be made for the presence of impurities, such as invert, moisture, and ash. The advantage of polarization is that it is rapid, easy, and very reproducible, having a precision of 0.001°. 

Dilution The reduction in concentration of a solute by the addition of solvent. 

Supersaturation An unstable condition in which the concentration of a solution or a vapor is greater than that corresponding to saturation. 

For any measurement of optical rotation, the wavelength of the light used and the temperature must both be specified. In this case, D refers to the d line of sodium at 589 nm and 25 refers to a measurement temperature of 25°C. Calculate the concentration of a solution of L-arginine that rotates the incident light by 0.35° in an optical path length of 1 dm (decimeter). 

The concentration of a solute has a considerable effect on the viscosity of the fluid and so on the surface convective resistance to heat flow. There is little published data on these effects, so applications need to be checked from basic principles. Industrial alcohol (comprising ethyl alcohol with a statutory addition of methyl alcohol to render it poisonous) may be used as a secondary refrigerant, either at 100% concentration or mixed with water. The fluid has a low viscosity and good heat transfer, but is nowlittle used on account of its toxicity and the fire risk in high concentrations. Other nonfreeze heat transfer fluids are used in specialist trades. 

Molality and Activities on the Molality Scale. In order to give a numerical value to the concentration of a solution, it is customary to... 

The concentration of a solute in solution can be expressed in terms of its molarity ... 

The pH of a solution can be measured by an instrument called a pH meter. A pH meter translates the H+ ion concentration of a solution into an electrical signal that is converted into either a digital display or a deflection on a meter that reads pH directly (Figure 13.4). Later, in Chapter 18, we will consider the principle on which the pH meter works. 

The hydrogen ion concentration of a solution of a hydrolysed salt can be readily calculated. The amounts of HA and of OH - ions formed as a result of hydrolysis are equal therefore, in a solution of the pure salt in water, [HA] = [OH-]. If the concentration of the salt is cmolL-1, then ... 

Example 11. Calculate (i) the hydrolysis constant, (ii) the degree of hydrolysis, and (iii) the hydrogen ion concentration of a solution of sodium acetate (0.01 mol L-1) at the laboratory temperature. 

As shown above the sulphide ion concentration of a saturated aqueous solution of hydrogen sulphide may be controlled within wide limits by suitably changing the concentration of hydrogen ions—a common ion—of the solution. In a like manner the hydroxide ion concentration of a solution of a weak base, such as aqueous ammonia (Kb = 1.8 x 10-5), may be regulated by the addition of a common ion, e.g. ammonium ions in the form of the completely dissociated ammonium chloride. The magnitude of the effect is best illustrated by means of an example. In a 0.1M ammonia solution, the degree of dissociation is given (Section 2.13) approximately by. 

To measure the hydrogen ion concentration of a solution the glass electrode must be combined with a reference electrode, for which purpose the saturated calomel electrode is most commonly used, thus giving the cell ... 

The detection limit is another value which is often quoted, and this may be defined in a variety of ways. The most widely accepted definition is that the detection limit is the smallest concentration of a solution of an element that can be detected with 95 per cent certainty. This is the quantity of the element that gives a reading equal to twice the standard deviation of a series of at least ten determinations taken with solutions of concentrations which are close to the level of the blank. 

One of the most important areas of application of heat transfer to boiling liquids is in the use of evaporators to effect an increase in the concentration of a solution. This topic is considered in Volume 2. 

The molarity (molar concentration) of a solute in a solution is the amount of solute in moles divided by the volume of the solution in liters. 

A common laboratory technique for determining the concentration of a solute is titration (Fig. L.2). Titrations are usually either acid-base titrations, in which an acid reacts with a base, or redox titrations, in which the reaction is between a reducing agent and an oxidizing agent. Titrations are widely used to monitor water purity and blood composition and for quality control in the food industry. 

The profile of the concentration of a solute in both the mobile and stationary phases is Gaussian in form and this will be shown to be true when dealing later with basic chromatography column theory. Thus, the flow of mobile phase will slightly displace the concentration profile of the solute in the mobile phase relative to that in the stationary phase the displacement depicted in figure 1 is grossly exaggerated to demonstrate this effect. It is seen that, as a result of this displacement, the concentration of solute in the mobile phase at the front of the peak exceeds the equilibrium concentration with respect to that in the stationary phase. It follows that there is a net transfer of solute from the mobile phase in the front part of the peak to the... 

This application is designed to model the influence of various concentrations of a solute near one edge of the membrane, on the diffusion of water through the membrane. Specifically we are interested in determining whether the model reveals a difference in the flow of water out of one compartment relative to the other. It is well known that if a semipermeable membrane is impervious to a solute on one side of a membrane, a greater flow of water from the other side will occur. This is a model of the osmotic effect, the flow of water through the... 

C04-0097. A student wishes to determine the concentration of a solution of HCl. The student adds 10.00 mL of the HCl solution to 150 mL of water, adds an indicator, and titrates with 0.0965 M NaOH. If the titration requires 32.45 mL of base, what is the concentration of the HCl solution ... 

If the concentration of a solute is lower than its solubility, additional solute can dissolve, but once the concentration of solute reaches the solubility of that substance, no further net changes occur. Individual solute molecules still enter the solution, but the solubility process is balanced by precipitation, as Figure 12-6 illustrates. A saturated solution in contact with excess solute is in a state of dynamic equilibrium. For eveiy molecule or ion that enters the solution, another returns to the solid state. We represent d Tiamic equilibria by writing the equations using double arrows, showing that both processes occur simultaneously ... 

The theoretical results described have implications for the design of experimental approaches for the study of transfer processes across the interface between two immiscible phases. The current response in SECMIT is clearly sensitive to the relative diffusion coefficients and concentrations of a solute in the two phases and the kinetics of interfacial transfer over a wide range of values of these parameters. 

Expressing the hydrogen ion concentration of a solution by a logarithmic function, such as the pH, is helpful in another way too many physicochemical properties of these solutions are linearly proportional to the logarithm of the hydrogen ion concentration. 

Acoustic cavitation increases a rate of mass transfer toward or from a solid surface. When a solute gradually diffuses onto a solid surface as in the case of electrolysis, a diffusion layer is formed near the solid surface in which the concentration of a solute changes from the saturated one at the solid surface to nearly the ambient one at the edge of the layer. A similar diffusion layer is formed when the solid material gradually dissolves into the liquid. Acoustic cavitation makes a diffusion layer... 

EXAMPLE 10.5. What is the concentration of a solution containing 6.35 mmol in LOOmL ... 

Two questions should immediately arise, (a) How can you know exactly when to stop the titration so that the number of moles of NaOH is equal to the number of moles of HCI (b) What is the use of determining the concentration of a solution of NaOH when the NaOH has now been used up reacting with the HCI (a) An indicator is used to tell us when to stop the titration. Typically an indicator is a compound that is one color (or colorless) in an acidic solution and a second color in a basic solution. Thus, we add NaOH slowly, drop by drop toward the end, until a permanent color change takes place. At that point, the end point has been reached, and the titration is complete. The HCI has just been used up. (b) The purpose of doing a titration is to determine the concentration of a solution. If the concentration of a liter of NaOH is to be determined, a small portion of it is used in the titration. The rest has the same concentration, and although the part used in the titration is no longer useful, the concentration of the bulk of the solution is now known. 

The concentration of a solution can be determined using a procedure known as titration. A carefully measured volume of the solution being analysed is reacted completely with another solution of accurately known concentration and volume. The concentration of the former solution can then be found, from a knowledge of the reaction occurring between the two substances. 

Alternatively, the concentration of a solution can be expressed in grams per dm3, in which case ... 

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