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SOLUBILITY

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The solubility of a solute is the maximum quantity of solute that can dissolve in a certain quantity of solvent or quantity of solution at a specified temperature.

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- is the property of a SOLID, LIQUID, or GASEOUS chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution of the solute in the solvent

SOLUBILITY

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The extent of the solubility of a substance in a specific solvent is measured as the saturationconcentration where adding more solute does not increase the concentration of the solution

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FACTORS AFFECTING SOLUBILITY

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the nature of the solute and solvent -

While only 1 gram of lead (II) chloride can be dissolved in 100 grams of water at room temperature, 200 grams of zinc chloride can be

dissolved. The great difference in the solubilities of the of these two substances is the the result of differences in their natures.

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Petroleum jelly will dissolve in gasoline because both petroleum jelly and gasoline are hydrocarbons.

In order for a solvent to dissolve a solute, the particles of the solvent must be able to separate the particles of the solute and occupy the intervening spaces. Polar solvent molecules can effectively separate the molecules of other polar substances. This happens when the positive end of a solvent molecule approaches the negative end of a solute molecule. A force of attraction then exists between the two molecules. The solute molecule is pulled into solution when the force overcomes the attractive force between the solute molecule and its neighboring solute molecule. Ethyl alcohol and water are examples of polar substances that readily dissolve in each other.

Solubility and the nature of a solvent and a solute:

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Petroleum jelly will not, on the other hand, dissolve in alcohol or water, since the polarity of these solvents is too high.

A popular aphorism used for predicting solubility is "like dissolves like“. The overall solvation capacity of a solvent depends primarily on its polarity

Sugar will not dissolve in gasoline, since sugar is too polar in comparison with gasoline. These can therefore be separated by filtration or extraction with water

Castor oil is soluble in oil

Sugar, is most soluble in alcohol, soluble in water, and slightly soluble in oil.

•non-polar solutes dissolve in non-polar solvents •Paraffin wax (C30H62) is a non-polar solute that will dissolve in non-polar solvents like oil, hexane (C6H14) or carbon tetrachloride (CCl4). •Paraffin wax will NOT dissolve in polar solvents such as water (H2O) or ethanol (ethyl alcohol, C2H5OH).

The solubility of vegetable oils in aqueous ethanol depends on the concentration of alcohol and temperature of the system. At ordinary temperatures even absolute alcohol is not a good solvent for vegetable oils since the solubility is even less than 10 g. of oil per 100 g. of alcohol. Mowrah, safflower, peanut, and cottonseed oils are soluble in absolute alcohol at 70°C

All the oils investigated are found to be miscible above the boiling point of alcohol even if the concentration is 98%. In 95% ethanol they are miscible between 90° and 100°C. Addition of a good solvent, like n-hexane, increases the solubility of oils, and the solubility temperatures are lowered.

polar solutes such as glucose (C6H12O6) will dissolve in polar solvents such as water (H2O) or ethanol (ethyl alcohol, C2H5OH) as the partially positively charged atom of the solute molecule is attracted to the partially negatively charged atom of the solvent molecule, and the partially negatively charged atom of the solute molecule is attracted to the partially positively charged atom of the solvent molecule.

Glucose or sugar will NOT dissolve in non-polar solvents such as oil, hexane (C6H14) or carbon tetrachloride (CCl4).

This statement indicates that a solute will dissolve best in a solvent that has a similar chemical structure to itself.

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Example, a very polar hydrophilic solute such as urea is very soluble in highly polar water, less soluble in fairly polar methanol, and practically insoluble in non-polar solvents such as benzene.

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In contrast, a non-polar or lipophilic solute such as napthalene is insoluble in water, fairly soluble in methanol, and highly soluble in non-polar benzene.[13]

Naphthalene. Is very soluble in oil, not very soluble in alcohol, and insoluble in water.

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Naphthalene is very soluble in oil, not very soluble in alcohol, and insoluble in water.

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temperature --

Generally, an increase in the temperature of the solution increases the solubility of a solid solute.

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temperature -- For liquids and solid

solutes, increasing the temperature not only increases the amount of solute that will dissolve but also increases the rate at which the solute will dissolve.

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temperature -- For gases, the reverse is

true. An increase in

temperature decreases both solubility and rate of solution

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temperature -- For liquids and solid

solutes, increasing the temperature not only increases the amount of solute that will dissolve but also increases the rate at which the solute will dissolve.

http://en.wikipedia.org/wiki/File:Temperature_dependence_solublity_of_solid_in_liquid_water_high_temperature.svg

The chart shows solubility curves for some typical solid inorganic salts (temperature is in degrees Celsius

Many salts behave like potassium nitrate, potassium chloride and sodium chloride, and show a large increase in solubility with temperature.

A few solid solutes, however, are less soluble in warmer solutions like sodium sulfate.

NO3- - All nitrates are

soluble.Cl-- All chlorides are soluble except AgCl, Hg2Cl2, and PbCl2.SO4

2- - Most sulfates are soluble.

Solubility Rules

Exceptions include Hg2SO4, BaSO4, PbSO4, and SrSO4. They are insoluble

Solubility Rules

CO32- - All carbonates are

insoluble except NH4+ and those of the Group 1

elements. Ex :( Li, Na, K ).OH- - All hydroxides are insoluble except those of the Group 1 elements,

Solubility Rules

Ba(OH)2, and Sr(OH)2. Ca(OH)2 is slightly soluble.

S2- - All sulfides are insoluble except those of the Group 1 and Group 2 elements and NH4

+.

Solubility Rules

Br1-,

I1- - are soluble except AgBr, HgBr, PbBr2,Alkali metals ( Li, Na, K)Ammonium ion ( NH4 )+

Perchlorate ( ClO4 ) -1

Acetates except Ag, Hg, Bi3+

Solubility Rules

Some solutes (e.g. NaCl in water) exhibit solubility which is fairly independent of temperature.

A few, such as cerium(III) sulfate, become less soluble in water as temperature increases. This temperature dependence is sometimes referred to as "retrograde" or "inverse" solubility.

Occasionally, a more complex pattern is observed, as with sodium sulfate, where the less soluble decahydrate crystal loses water of crystallization at 32 °C to form a more soluble anhydrous phase.[

Solubility of Gases

vs. Temperature

As the temperature increases, the solubility of a gas decrease as shown by the downward trend in the graph .

Gaseous solutes exhibit more complex behavior with temperature. As the temperature is raised, gases usually become less soluble in water (to minimum which is below 120 °C for most permanent gases), but more soluble in organic solvents

The solubility of organic compounds nearly always increases with temperature. 8]

pressure - For solids and liquid solutes, changes in pressure have practically no effect on solubility.

For gaseous solutes, an increase in pressure increases solubility and a decrease in pressure decreases solubility. (When the cap on a bottle of soda pop is removed, pressure is released, and the gaseous solute bubbles out of solution. This escape of a gas from solution is called effervescence.)

pressure - The solubility of a gas in a solvent is directly proportional to the partial pressure of that gas above the solvent.

pressure - This relationship is written as:

where kH is a temperature-dependent constant (for example, 769.2 L•atm/mol for dioxygen (O2) in water at 298 K), p is the partial pressure (atm), and c is the concentration of the dissolved gas in the liquid (mol/L).

In the presence of small bubbles, the solubility of the gas does not depend on the bubble radius in any other way than through the effect of the radius on pressure

pressure - The solubility of gas in

the liquid in contact with small bubbles is increased due to pressure increase by Δp = 2γ/r

The rate of solution is a measure of how fast a substance dissolves. Some of the factors determining the rate of solution are:

size of the particles - When a solute dissolves, the action takes place only at the surface of each particle. When the total surface area of the solute particles is increased, the solute dissolves more rapidly. Breaking a solute into smaller pieces increases its surface area and hence its rate of solution

stirring -- With liquid and solid

solutes, stirring brings fresh portions of the solvent in contact with the solute, thereby increasing the rate of solution.

amount of solute already dissolved -- When there is little solute already in solution, dissolving takes place relatively rapidly. As the solution approaches the point where no solute can be dissolved, dissolving takes place more slowly.

Synthetic chemists often exploit differences in solubilities to separate and purify compounds from reaction mixtures, using the technique of liquid-liquid extraction

APPLICATION

The technique of recrystallization, used for purification of solids, depends on a solute's different solubilities in hot and cold solvent. A few exceptions exist, such as certain cyclodextrins]

APPLICATION