11.3 Solubility

Chapter 11 contains solutions and chloroids molecule of water.

There is a gas called pure hydrogen chloride.

There is no ion in this gas.
The solution of hydrogen chloride in water is a very good conductor.
Solutions of hydrogen chloride in many other solvents, such as benzene, do not conduct electricity and do not contain ion, because the water molecule plays an essential part in forming ion.

Weak acids and bases that only react when dissolved in water are classified as weak electrolytes.

The discussion of strong and weak acids in the earlier chapter of this text may be of interest to the reader.

By the end of this module, you will be able to: You can repeat this process until the salt concentration of the solution reaches its natural limit, a limit determined primarily by the relative strengths of the solute-solute, solute-solvent, and solvent-solvent attractive forces discussed in the previous two modules of this chapter.

No matter how long you stir the solution, undissolved salt remains.
The concentration of salt in the solution is known as its solubility.

One with a relatively high concentration of solute is called concentrated, while a solution with a relatively low concentration is called dilute.

If we add more salt to a saturated solution of salt, it will fall to the bottom.

The dissolved salt is represented by the forward direction of the dissolution equation.
Salt will form as depicted by the reverse direction of the equation.
The amount of dissolved and undissolved salt remains constant when the system is at equilibrium.
The number and size of the undissolved salt crystals will change over time, but their combined mass will remain the same, as support for the simultaneous occurrence of the dissolution and precipitation processes is provided.

This can be used to prepare various solutions.

The carbonated beverage in an open container that has not yet "gone flat" is supersaturated with carbon dioxide gas and will decrease until it reaches its equilibrium value.

This shows the precipitation of a supersaturated solution.

The effect of intermolecular attractive forces on solution formation was discussed in an earlier module of this chapter.

The chemical structures of the solute and solvent dictate the types of forces that can be achieved.

The water solubility of oxygen is three times greater than that of helium, but 100 times less than that of chloromethane.

Oxygen can be found in the liquid hydrocarbons C6H14, which is 20 times greater than it is in water.

The solubility of a substance in a solvent can be affected by other factors.

One of the factors with decreasing gas solubility is temperature.
This is one of the consequences of thermal pollution of natural bodies of water.

As the temperature increases, the solubilities of the gases in water decrease.

All solubilities were measured with a constant pressure of gas above the solutions.

The solubility of oxygen in the water is decreased when the temperature of a river, lake, or stream is raised.

Decreased levels of dissolved oxygen can cause serious consequences for the health of the water's ecosystems and can result in large-scale fish kills.

The partial pressure of solute in the gas to which the solution is exposed affects the solubility of a gaseous solute.

There is a nice illustration of this relationship.
The OpenStax book is free and can be used to seal the beverage container and expose the beverage to a high pressure of carbon dioxide.
When the beverage container is opened, a familiar hiss is heard as the carbon dioxide gas pressure is released, and some of the dissolved carbon dioxide is typically seen leaving solution in the form of small bubbles.

The quantity of an ideal gas is proportional to the pressure of the gas.

The concentration of dissolved oxygen in water exposed to gaseous oxygen at a partial pressure of 101.3 kPa is 1.38 x 10-3 mol L-1.

Henry's law can be used to determine the solubility of oxygen when its partial pressure is 20.7 kPa.

Various units may be used to express the quantities involved in these computations.

Any combination of units that yield to the constraints of the analysis is acceptable.

The dissolution of the solute was achieved by exposing a 100.0 mL sample of water to an atmosphere containing a gaseous solute at 20.26 kPa.

Henry's law can be used to determine the solubility of this gaseous solute when it has a pressure of 101.3 kPa.

The bends are an effect of the increased pressure of the air in the lungs of scuba divers when swimming underwater.

Divers experience an increase in pressure due to the water above them of 1 atm for each 10 m of depth.
Henry's law states that the concentrations of gases dissolved in the diver's blood are proportionally higher than those in the air.

The ambient pressure decreases as the diver ascends to the surface of the water.

If the ascent is too rapid, the gases escaping from the diver's blood can form bubbles that can cause a variety of symptoms.
Divers must ascend from depths at relatively slow speeds (10 or 20 m/min) or stop several times during the ascent to avoid DCS.
Hyperbaric oxygen therapy is provided to divers when preventive measures are unsuccessful.

When a chemical reaction takes place between the gaseous solute and the solvent, there are deviations from Henry's law.

The law states that the solubility of ammonia in water does not increase as rapidly with increasing pressure because ammonia, being a base, reacts to some extent with water to form ammonia ion and hydroxide ion.

Supersaturated solutions can be formed by gases.

If a solution of a gas in a liquid is prepared either at low temperature or under pressure, then as the solution warms or as the gas pressure is reduced, the solution may become supersaturated.
More than 1700 people were killed in 1986 when a cloud of gas, most likely carbon dioxide, bubbled from a deep lake in a volcanic crater.
The water at the bottom of the lake has a lot of carbon dioxide in it.
It is believed that the lake underwent a turnover due to gradual heating from below the lake and the warmer, less dense water reaching the surface.
Humans and animals living in the valley were suffocated by the dissolved CO2 that flowed down the valley below the lake.

Motor oil with gasoline is miscible.

The water and the antifreeze are notcible.

Liquids that mix with water in all proportions are usually polar substances.

The dipole-dipole attractions of the solute molecule with the solvent molecule are the same as they are in the pure solute or pure solvent.

The two kinds of molecule mix easily.
There is no difference in the strength of the solute-solute, solvent-solvent, and solute-solvent intermolecular attractions of nonpolar liquids.

When we pour liquids into a container, they form layers.

Many nonpolar liquids are immiscible with water.
The attraction between the polar water and non polar liquids is weak.
The water and nonpolar liquid are 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- Miscible liquids are of infinite mutual solubility, while immiscible liquids are of very low mutual solubility.

Water and oil are liquids.

The less dense oil will float on top of the water in the mixture of these two substances.

When mixed, two partially miscible liquids form two layers.

The upper and lower layers of the bromine and water mixture are saturated with bromine.

Solutions and chloroids were dissolved in it.

The dark color of the bromine layer is not affected by the low solubility of water in bromine.

The clear liquid in the middle is partially miscible.

The top layer of the mixture is a saturated solution of bromine in water, while the bottom layer is a saturated solution of water in bromine.
There are exceptions to the general trend of increasing solubility with temperature, as shown by the ionic compound cerium sulfate.

The graph shows how temperature changes the solubility of some objects.

Supersaturated solutions of certain compounds can be prepared by exploiting the temperature dependence of solubility.

A solution may be saturated with the compound at an elevated temperature and then cooled to a lower temperature without causing the solute.

The solution is relatively stable and contains solute at a concentration greater than its equilibrium solubility at the lower temperature.
Precipitation of the excess solute can be initiated by adding a seed crystal or mechanically agitated the solution.
The one pictured is a hand warmer.

The hand warmer produces heat when the solution has a high concentration of sodium acetate.