Solutions

Solutions : 

Solutions

Solvation : 

Solvation Water is an excellent solvent Solute dissolves in solvent to form solution Most solutions are solids dissolved in liquids Solid solute Liquid solvent Often water is solvent Aqueous solutions

Solvation : 

Solvation Process of solute dissolving in solvent Example – salt (NaCl) dissolving in water NaCl is an ionic crystal Ions of Na+ and Cl- arranged in a pattern Ions close together and vibrating Water is a covalently bonded molecule Water is polar (one end partly +, one end partly -) Molecules are vibrating and moving past one another

Slide 4: 

Casiday, Noelken, Frey. Treating the Public Water Supply: What Is In Your Water, and How Is It Made Safe to Drink?, Sept. 5, 2008. Department of Chemistry, Washington University, St. Louis, MO. March 18, 2009. http://www.chemistry.wustl.edu/~edudev/LabTutorials/Water/PublicWaterSupply/PublicWaterSupply.html

Solvation : 

Solvation Process of ions being pulled away from their solid lattice and distributed in the solution. A solute that dissolves is soluble. A solute that does not dissolve is insoluble.

Solvation of Ionic Compounds : 

Solvation of Ionic Compounds Polarity determines how well solute will dissolve “Like dissolves like.” Polar solvents dissolve polar and ionic solutes. Water is polar. Ionic compounds generally dissolve well in water.

Solvation of Ionic Compounds : 

Solvation of Ionic Compounds Ionic compounds fall apart when they dissolve, separating the positive cations from the negative anions. Dissociation NaCl(s)  Na+(aq) + Cl-(aq)

Solvation of Ionic Compounds : 

Solvation of Ionic Compounds Once dissociated, ions are free to move about in the solution. Ions can carry charge from one part of the solution to another. The solution can conduct electricity. The ionic compound is an electrolyte. Most ionic compounds are electrolytes.

Solvation of Molecular Compounds : 

Solvation of Molecular Compounds Molecules do not dissociate Molecules separate from one another in the crystal C12H22O11(s)  C12H22O11(l) Non-electrolytes (do not conduct electricity)

Solutions of two liquids : 

Solutions of two liquids Miscible Immiscible Most molecular liquids DO NOT dissolve in water – oil, gasoline Most molecular liquids DO dissolve in oil – gasoline, kerosene Molecular liquids that do dissolve in water are polar molecules - alcohols

Cleaning by dissolving : 

Cleaning by dissolving Use water or a polar substance to dissolve or clean polar substances – salts, residues, some “dirt” Use oil or a non-polar substance to dissolve or clean nonpolar substances – grease, oil, grime

Cleaning by dissolving : 

Cleaning by dissolving Soap is both polar and non-polar, so works well with water. Non-polar end of the molecule dissolves grease, oil, grime Polar end of the molecule dissolves in the water Polar portion Non-polar portion

Factors Affecting Solvation : 

Factors Affecting Solvation To speed up the dissolving process: Heat it Crush it Stir it

Saturated Solutions and Solubility : 

Saturated Solutions and Solubility Unsaturated – More solute could dissolve in this solution.

Saturated Solutions and Solubility : 

Saturated Solutions and Solubility Saturated – No more solute could dissolve in this solution.

Saturated Solutions and Solubility : 

Saturated Solutions and Solubility Supersaturated – Too much solute is dissolved in this solution.

Making a supersaturated solution : 

Making a supersaturated solution

Solubility : 

Solubility Amount of solute that dissolves in a certain amount of solvent (most often 100 grams) to create a saturated solution at a given temperature and pressure. Solubility Curve

Solubility of a Solid : 

Solubility of a Solid Most solids increase in solubility as the temperature of the solvent is raised. Some show a decrease They are rare

Solubility of a Gas : 

Solubility of a Gas Most gases decrease in solubility as the temperature of the solvent is raised. Pressure affects the solubility of a gas, too. Lower pressures lead to lower solubility at constant temperatures

Gas Solubility : 

Gas Solubility Pressure constant

Biology/Ecology : 

Biology/Ecology If temperature of a body of water increases, the solubility of the oxygen in the water decreases. How can that affect wildlife? Solubility of carbon dioxide in water also decreases with increasing temperature. How can that explain the relationship of carbon dioxide and global warming?

Colloids : 

Colloids Particles dispersed, not dissolved Particles are so small they do not settle out

Tyndall Effect : 

Tyndall Effect

Suspensions : 

Suspensions Larger particles Settle upon standing