SOLUBILITY Objectives: * Understand the difference between Unsaturated, Saturated, and Supersaturated. * Understand how to read Solubility Curves. * Understand how to solve Percent Concentration Problems.

Solubility curve Saturated Unsaturated Supersaturated

Solubility curve Any point on a line represents a saturated solution. In a saturated solution, the solvent contains the maximum amount of solute. Example: At 90 o C, 40 g of NaCl in 100g H 2 O represent a saturated solution.

Solubility curve Any point below a line represents an unsaturated solution. In an unsaturated solution, the solvent contains less than the maximum amount of solute. Example: At 90 o C, 30 g of NaCl in 100g H 2 O represent an unsaturated solution. 10 g of NaCl will have to be added to make the solution saturated.

Solubility Curve Any point above a line represents a supersaturated solution. In a supersaturated solution, the solvent contains more than the maximum amount of solute. A supersaturated solution is very unstable and the amount in excess can precipitate or crystallize. Example: At 90 o C, 50 g of NaCl in 100g H 2 O represent a supersaturated solution.

Solubility curve Any solution can be made saturated, unsaturated, or supersaturated by changing the temperature.

In a few instances (e.g., Li 2 SO 4 below) the solubility of the salt will decrease with temperature. This observation does not invalidate the above explanantion but rather suggests that several competing ideas need to be taken into account to fully understand chemical processes.

Solubility of Gases vs. Temperature The variation of solubility for a gas with temperature can be determined by examining the graph below: As the temperature increases, the solubility of a gas decreases as shown by the downward trend in the graph.

Units of Concentrations The grams of solute per grams of solution equals the Percent Concentration. = Percent Concentration solute solution x 100

How do I get sugar to dissolve faster in my iced tea? Stir, and stir, and stir Add sugar to warm tea then add ice Grind the sugar to a powder

Nature of the solute and solvent “Likes dissolve likes” When two similar liquids - here water and methanol- are mixed, the molecules are intermingled. The mixture has a more disorderly arrangement of molecules than the separate liquids. It is this disordering process that largely drives solution formation. polar solute/polar solvent: EX: ethanol, salt, sugar in water nonpolar solute/nonpolar solvent: EX: Iodine in carbontetrachloride, gasoline or benzene

Electrolyte and Non-electrolyte Electrolyte: a substance that conducts electricity when dissolved in water. –Acids, bases and soluble ionic solutions are electrolytes. Non-electrolyte: a substance that does not conduct electricity when dissolved in water. –Molecular compounds and insoluble ionic compounds are non-electrolytes.

Electrolytes Allows an electric charge to be carried.

Types of solutes Na + Cl - Electrolyte Conducts electricity

Types of solutes sugar Nonelectrolyte Does not conduct electricity