Solubility

Chapter 15.1 B

Vocabulary Word

• Solubility: the maximum amount of solute that dissolves in a given amount of solvent at a specific temperature and pressure

Solubility

• Every solute has a characteristic solubility

Solubilities of some solutes in water at varioustemperatures

Substance Solubility (g/100 g H2O)0oC 20oC 60oC 100oC

aluminum sulfate 31.2 36.4 59.2 89.0ammonium chloride 29.4 37.2 55.3 77.3barium hydroxide 1.67 3.89 20.94 -barium nitrate 4.95 9.02 20.4 34.4calcium hydroxide 0.189 0.173 0.121 0.076lead (II) chloride 0.67 1.00 1.94 3.20lithium sulfate 36.1 34.8 32.6 -potassium chloride 28.0 34.2 45.8 56.3potassium sulfate 7.4 11.1 18.2 24.1sodium chloride 35.7 35.9 37.1 39.2

Solvation

• Particles of solvent collide with particles of solute dissolving

• As more and more solute dissolves, some of the dissolved solute particles collide with the remaining crystalline solute crystallization

Solvation

• As long as dissolving rate > crystallization rate more solute will continue to dissolve (unsaturated solution)

• Eventually dissolving rate = crystallization rate (dynamic equilibrium: saturated solution)

Factors Affecting Solubility

• Solubility is how much solute will dissolve (NOT how fast it dissolves)– Temperature– Pressure

Temperature Effects

• Many substances are more soluble at higher temperature– More sugar or salt will dissolve in hot liquid

than in cold liquid

Temperature Effects

• Gases are less soluble at higher temperatures– As the temperature increases the kinetic

energy increases. This allows gas particles to escape to the atmosphere

Temperature Effects

Supersaturated Solutions

• Since solubility of some solids increases with temperature:– Allows the formation of supersaturated

solutions– Make a saturated solution at an elevated

temperature– Cool slowly

Vocabulary Word

• Supersaturated solution: a solution that contains more dissolved solute than a saturated solution at the same temperature.

Supersaturated Solutions

• Are unstable– Add a seed of solute crystallization

Supersaturated Solutions

• Are unstable– Will crystallize on scratches of the container– Will crystallize if tapped or stirred

Examples of Supersaturated solutions

• Cloud seeding: silver iodine is spread in the atmosphere to cause water particles in supersaturated air to condense and rain to fall

Examples of Supersaturated solutions

• Mineral springs have salt crystals along the edge

Examples of Supersaturated solutions

• Rock candy is made using a supersaturated solution of sugar water

Pressure Effects on Solubility

• Solubility of gaseous solutes increase with increasing pressure (the soft drink won’t go flat as quickly if the lid is kept on)

Pressure Effects on Solubility

• Soft drinks are carbonated at high pressure

• When the cap is unscrewed, gas escapes

Spangler Video Clip

• supersaturated solutions:– http://www.stevespanglerscience.com/

experiment/00000078

Vocabulary Word

• Henry’s law: the solubility of a gas in a liquid is proportional to the pressure of the gas above the liquid

S1 = S2 solubility at pressure 1

P1 P2 solubility at pressure 2

Henry’s Law

• Is used to determine the solubility at different pressures