Solubility is the relative ability of a solute (solid, liquid, or gas) to
dissolve into a solvent and form a solution.
LEARNING OBJECTIVES [ edit ]
Recognize the various ions that cause a salt to generally be soluble/insoluble in water.
Define the chemical concept of solubility.
KEY POINTS [ edit ]
Solubility is the relative ability of a solute to dissolve into asolvent.
Several factors affect the solubility of a given solute in a given solvent. Temperature often plays
the largest role, althoughpressure can have a significant effect for gases.
To predict whether a compound will be soluble in a given solvent, remember the saying, "Like
dissolves like." Highlypolar ionic compounds such as salt readily dissolve in polar water, but do
not readily dissolve in non­polar solutions such as benzene or chloroform.
TERMS [ edit ]
solute
the compound that dissolves in solution (can be a solid,liquid, or gas)
solvent
the compound (usually a liquid) that dissolves the solute
solubility
the relative ability of a solute to dissolve into a solvent
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Definition of Solubility
Solubility is the ability of a solid, liquid, or gaseous chemicalsubstance (referred to as
the solute) to dissolve in solvent(usually a liquid) and form a solution. The solubility of a
substance fundamentally depends on the solvent used, as well as temperature and pressure.
The solubility of a substance in a particular solvent is measured by theconcentration of
the saturated solution. A solution is considered saturated when adding additional solute no
longer increases the concentration of the solution.
The degree of solubility ranges widely depending on the substances, from infinitely soluble
(fully miscible), such as ethanol in water, to poorly soluble, such as silver chloride in water.
The term "insoluble" is often applied to poorly solublecompounds. Under certain conditions,
the equilibriumsolubility can be exceeded, yielding a supersaturated solution.
Solubility does not depend on particle size; given enough time, even large particles will
eventually dissolve.
Factors Affecting Solubility
Temperature
The solubility of a given solute in a given solvent typically depends on temperature. For
many solids dissolved in liquid water, solubility tends to correspond with increasing
temperature. As water molecules heat up, they vibrate more quickly and are better able to
interact with and break apart the solute.
Solubilty of various substances vs. temperature change
Solubility increases with temperature for most substances; for example, more sugar will dissolve in hot
water than in cold water.
The solubility of gases displays the opposite relationship with temperature; that is, as
temperature increases, gas solubility tends to decrease. In a chart of solubility vs.
temperature, notice how solubility tends to increase with increasing temperature for
the salts and decrease with increasing temperature for the gases.
Pressure
Pressure has a negligible effect on the solubility of solid and liquid solutes, but it has a strong
effect on solutions with gaseous solutes. This is apparent every time you open a soda can; the
hissing sound from the can is due to the fact that its contents are under pressure, which
ensures that the soda stays carbonated (that is to say, that the carbon dioxide stays dissolved
in solution). The takeaway from this is that the solubility of gases tends to correlate with
increasing pressure.
Polarity
A popular saying used for predicting solubility is "Like dissolves like." This statement
indicates that a solute will dissolve best in a solvent that has a similar chemical structure; the
ability for a solvent to dissolve various compounds depends primarily on its polarity. For
example, apolar solute such as sugar is very soluble in polar water, less soluble in moderately
polar methanol, and practically insoluble in non­polar solvents such as benzene. In contrast,
a non­polar solute such as naphthalene is insoluble in water, moderately soluble in
methanol, and highly soluble in benzene.
Solubility Chart
The solubility chart shows the solubility of many salts. Salts of alkali metals (and
ammonium), as well as those of nitrate and acetate, are always soluble. Carbonates,
hydroxides, sulfates, phosphates, and heavy metal salts are often insoluble.
Solubility chart
The solubilities of salts formed from cations on the left and anions on the top are designated as: soluble
(S), insoluble (I), or slightly soluble (sS).
Solubility
Solubility of salt and gas solutes in liquid solvent.