Solutes molar solubility

Now we can employ equation 19.4 to calculate the molar solubility of Mg(OH)2 in the buffer solution Molar Solubility Mg(OH)2 = [Mg2+]equii... 

The solubility is the quantity of a substance that dissolves in a certain quantity of water. In solubility equilibria calculations, it is usually expressed as grams of solute per liter of solution. Molar solubility is the number of moles of solute per liter of solution. 

It is convenient to define the solubility of ionic substances in units of g per 1000 g of saturated solution, or as the number of moles of substance needed to produce 1 dm of saturated solution. Molar solubility is defined as follows ... 

The reverse of Example 16.4 involves finding Rq, of a compound given its solubility. The solubilities of many ionic compounds are determined experimentally and tabulated in chemical handbooks. Most solubility values are given in grams of solute dissolved in 100 grams of water. To obtain the molar solubility in moles/L, we have to assume that the density of the solution is equal to that of water. Then the number of grams of solute per 100 g water is equal to the number of grams of solute per 100 mL of solution. This assumption is valid because the mass of the compound in solution is small. To solve for IQp, find the molar solubility of the solute and determine the concentration of its component ions. Substitute into the IQp expression. 

If we add only a small amount—20 g, for instance—of glucose to 100 mL of water at room temperature, it all dissolves. However, if we add 200 g, some glucose remains undissolved (Fig. 8.16). A solution is said to be saturated when the solvent has dissolved all the solute that it can and some undissolved solute remains. The concentration of solid solute in a saturated solution has reached its greatest value and no more can dissolve. The molar solubility, s, of a substance is its molar concentration in a saturated solution. In other words, the molar solubility of a substance represents the limit of its ability to dissolve in a given quantity of solvent. 

The molar solubility of a substance is its molar concentration in a saturated solution. A saturated solution is one in which the dissolved and undissolved solute are in dynamic equilibrium with each other. 

One of the simplest ways to determine fCsp is to measure the molar solubility of the compound, the molar concentration of the compound in a saturated solution,... 

Experimentally, fCsp = 1.6 X 10 10 at 25°C, and the molar solubility of AgCl in water is 1.3 X 10 5 mol-IT. If we add sodium chloride to the solution, the concentration of Cl ions increases. For the equilibrium constant to remain constant, the concentration of Agf ions must decrease. Because there is now less Ag+ in solution, the solubility of AgCl is lower in a solution of NaCl than it is in pure water. A similar effect occurs whenever two salts having a common ion are mixed (Fig. 11.16). 

Because 1 mol AgCI — 1 mol Cl, the molar solubility of AgCl is given by the equation s = [Cl ]. From the balanced overall equation, we see that [Cl-] = [Ag(NH )2+l in the saturated solution. The equilibrium table, with all concentrations in moles per liter, is... 

Use the data in Table 11.4 to calculate the molar solubility of each sparingly soluble substance in its respective solution ... 

A classic pharmaceutical science textbook might have defined poor solubility as anything below a solubility of 1 g mL-1 (2 mol L-1 solution for a molecular weight of 500 Da) at pH 6.5 (or pH 7). This classic view is reflected in the Chemical Abstracts SciFinder 2001 solubility range definitions for solubility calculated using Advanced Chemistry Development (ACD) Software Solaris V4.67. These semi-quantitative ranges for molar solubility are very soluble, 1 mol L 1 < solubility soluble, 0.1 mol L 1 < solubility < 1 mol L 1 slightly soluble, 0.01 mol L 1 <... 

The molar solubility of a compound is the number of moles of the compound that dissolve to produce one liter of saturated solution. 

In problem type (1), there is a physical relationship between ions. For PbCl2, the concentration of Cl- ions in solution are twice the concentration of Pb2+ ions because they come from the same source, the solid PbCl2. The molar solubility of PbCl2, s, is equal to [Pb2+], so [Cl-] = 2s, twice the molar solubility. So, Ksp = [Pb2+][C1-]2 = (s)(2sf. Some students get the mistaken impression that the concentration of Cl- is doubled, but it is the molar solubility that must be doubled to equal the Cl- concentration. 

In other words, the solubility of a solute indicates how much of that solute is present in a solution at equilibrium. Data tables often express solubility as (g solute)/(100 mL solvent). Molar solubility, on the other hand, is always expressed in terms of (mol solute/L solvent). 

The molar solubility of PbCr04 in a solution of 0.10 mol/L Na2Cr04 is 2.3 x 10 mol/L. Your prediction was correct. The solubility of PbCr04 decreases in a solution of common ions. 

In this section, you determined the solubility product constant, Kgp, based on solubility data. You obtained your own solubility data and used these data to calculate a value for Kgp. You determined the molar solubility of ionic solutions in pure water and in solutions of common ions, based on their Ksp values. In section 9.3, you will further explore the implications of Le Chatelier s principle. You will use a reaction quotient, Qsp, to predict whether a precipitate forms. As well, you will learn how selective precipitation can be used to identify ions in solution. 

Explain how to calculate the molar solubility of a pure substance in water or in a solution of a common ion, given Kgp. 

The particular case of the solubilities of organic solutes in water can be dealt with by rather simple equations, based on a general equation for solvent-dependent properties, apphed to solubilities, distribution ratios, rate constants, chromatographic retention indices, spectroscopic quantities, or heats of association [4] [see Eq. (2.12) for an example of its application]. For the molar solubilities of (liquid) aliphatic solutes B in water at 25°C the equation... 

The number of mole of dissolved salt in a one liter solution in the saturated solution is known as molar solubility. It can be represented as s . It is not difficult to find the solubility product of a salt by knowing its molar solubility. For example, the molar solubility of CaS04 at 20 °C is 1.5 10 mol/L. This signifies that the concentration of each of the ions Ca and SO is 1.5 10 mol/L in a saturated solution of CaSO.. 

What is the molar solubility of Cap2 salt in 0.1 M CaCl2 solution ... 

A reactor charged with 4,4 -diphenylether-dicarboxylic acid, hydrazinesulfate, and polyphosphoric acid were mixed and reacted for 1 hour at 160°C and then further heated to 180°C. This mixture was then treated with 4-aminobenzenesulfonic acid and heated for an additional 2 hours. The molar solubility ratio of polyphosphoric acid/hydrazinesulfate and the molar monomer ratio ofhydrazinesulfatc/4,4 -dipheny-lether-dicarboxylic acid were kept constant at 10 and 1.2, respectively. The mixture was further treated with sufficient 4-aminobenzenesulfonic acid so that the molar ratio of in situ formed polyhydrazide was maintained at 1 1. After heating was stopped, the mixture was poured into warm water containing 5 wt% sodium hydroxide solution and a dark blue fiber obtained. The fiber was washed in distilled water and then dried in a vacuum furnace for 48 hours at 100°C. The dried material had a nitrogen/carbon ratio of 0.174 and a sulfur/carbon ratio of 0.058. The product had an Mw of... 

The Kelvin equation may also be applied to the equilibrium solubility of a solid in a liquid. In this case the ratio p/p0 in Equation (40) is replaced by the ratio a/a0, where a0 is the activity of dissolved solute in equilibrium with a flat surface, and a is the analogous quantity for a spherical surface. For an ionic compound having the general formula MmXn, the activity of a dilute solution is related to the molar solubility S as follows ... 

One of the simplest ways to determine Ksp is to measure the molar solubility of the compound, the molarity of the compound in a saturated solution, but more advanced and accurate methods are also available. Table 11.5 gives some experimental values. In the following calculations, we use s to denote the numerical value of the molar solubility expressed in moles per liter for example, if the molar solubility of a compound is 6.5 X 10 s moFL-1, we write s = 6.5 X 10-5. 

STRATEGY As usual, we begin by writing the chemical equation for the solubility equilibrium and the expression for Ksp. The molar solubility is the molarity of formula units in the saturated solution. Because each formula unit produces a known number of cations and anions in solution, we can express the molarities of the cations and anions in terms of s. Then we express Ksp in terms of s and solve for s. Assume complete dissociation. 

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